JPH0815659A - Production of active matrix substrate - Google Patents

Abstract

PURPOSE:To make it possible to form source and drain electrodes by self- alignment to the gate electrodes of switching transistors, thereby making it possible to prevent overlap of the gate electrodes and the drain electrodes in a vertical direction which is the cause for flickering and screen printing when image display is made. CONSTITUTION:Plural scanning signal lines 2 projectingly provided with the gate electrodes 2 are formed on a transmissive substrate 1. These scanning signal lines 2 are coated with insulating films 3 and semiconductor films 4 to 6 are formed on the gate electrode parts of the insulating films 3 and are patterned to island shapes; thereafter, a transparent conductive film 7 extending from the surface of the semiconductor films to the adjacent scanning signal lines is formed. After a photoresist 8 is applied to the transparent conductive film, the photoresist 8 is exposed from the rear surface side of the transmissive substrate 1 and from the front side of the transmissive substrate 1 via a photomask 10 for shielding light of the semiconductor film parts. The transparent conductive film 7 of the unexposed parts of the photoresist mask 8 and the semiconductor films 4 to 6 are partly removed.

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, and more particularly to a method for manufacturing an active matrix substrate used in a liquid crystal display device or the like.

[0002]

2. Description of the Related Art A conventional active matrix substrate is shown in FIG.
0 is shown. In FIG. 10, 2a is aluminum (A
1) a gate electrode made of tantalum (Ta) or the like, 3 is silicon nitride (SiN _x ) or silicon oxide (SiO _x )
And the like, insulating films 4, 5 are semiconductor films containing no semiconductor impurities, 6 are semiconductor films containing semiconductor impurities, 7
a is molybdenum silicide (MoSi) and aluminum (A
1) is a two-layer source electrode made of, for example, 7b is a drain electrode made of the same material as the source electrode 7a, and 7c is a pixel electrode made of a transparent conductive film.

The gate electrode 2a, the insulating film 3, the semiconductor film 4,
A switching transistor is formed of the source / drain electrodes 5 and 6, and a pixel electrode 7c made of a transparent conductive film such as ITO is connected to the drain electrode 7b of the switching transistor. That is, a scanning signal is supplied to the gate electrode 2a to control ON / OFF of the switching transistor. Further, when the image signal is supplied to the source electrode 7a and the switching transistor is in the ON state, the image signal is supplied to the pixel electrode 7c. This image signal is configured such that positive and negative signal voltages are alternately applied with the voltage applied to the counter electrode (not shown) as a central value.

[0004]

In this conventional active matrix substrate, a gate electrode 2a and a pixel electrode 7c are formed on a transparent substrate 1 made of glass or the like, and an insulating film 3 is formed on the gate electrode 2a. , The semiconductor films 4, 5 and 6 are sequentially stacked and patterned in an island shape, and the source / drain electrodes 7 are further sequentially stacked and formed, and then the source / drain electrodes 7 facing the gate electrode 2a are formed.
By etching away the semiconductor film 6 containing semiconductor impurities, a switching transistor is formed.

In this conventional method, when the source / drain electrode 7 and the semiconductor film 6 containing a semiconductor impurity are divided by etching, a photoresist (not shown) is applied to the surface of the source / drain electrode 7 to form a transparent film. A photomask is arranged on the front surface side of the light-transmissive substrate 1, and a photoresist is exposed from the front surface side of the light-transmissive substrate 1 to remove a part of the source / drain electrodes 7 and the semiconductor film 6 containing semiconductor impurities by etching. Was there.

Therefore, a part (ΔL) of the source / drain electrode 7 and the gate electrode 2a overlap each other in the vertical direction due to the alignment accuracy of the photomask, and as a result, the gate electrode 2a and the drain electrode 7b of the switching transistor are placed between them. A parasitic capacitance C _gd is generated, and the positive and negative polarities applied to the pixel electrode 11 as a whole fall below the central value of the voltage applied to the counter electrode to the negative polarity side, and flicker occurs when an image is displayed. There is a problem that image sticking occurs.

The present invention has been made in view of the above problems of the prior art, and prevents the source / drain electrodes and the gate electrode from overlapping in the vertical direction as much as possible, so that the gate electrode of the switching transistor is formed. Avoid the occurrence of parasitic capacitance between the drain electrode and
An object of the present invention is to provide a method for manufacturing an active matrix substrate in which flicker and image sticking do not occur when an image is displayed.

[0008]

In order to achieve the above-mentioned object, in the method for manufacturing an active matrix substrate according to the present invention, a plurality of scans each composed of a light shielding member provided with a gate electrode protruding on a transparent substrate. A signal line is formed, the scanning signal line is covered with an insulating film made of a translucent member, and the gate electrode portion on the insulating film extends to the semiconductor film and the scanning signal line extending from the semiconductor film to the adjacent scanning signal line. Forming a transparent conductive film and applying a photoresist on the transparent conductive film, and then transmitting the light to the photoresist from the back surface side of the transparent substrate and through a photomask that shields the semiconductor film portion. The surface of the flexible substrate is exposed to light, and the transparent conductive film and a part of the semiconductor film in the non-exposed portion of the photoresist are removed.

[0009]

As described above, when the transparent conductive film serving as the source / drain electrodes is formed on the semiconductor film and the photoresist is applied, when the light is irradiated from the back side of the transparent substrate, the self alignment with the gate electrode is performed. Then, the photoresist is exposed to light so that a part of the semiconductor film and the source / drain electrodes can be divided, and thus the gate electrode and the drain electrode of the switching transistor can be prevented from overlapping in the vertical direction as much as possible.

Further, if the photoresist is exposed only from the back surface side of the transparent substrate, the photoresist on the adjacent scanning signal line is not exposed. However, as described above, the photoresist is shielded through the photomask that shields the semiconductor film portion. When the light is also exposed from the front surface side of the optical substrate, the photoresist on the adjacent scanning signal line can be exposed without exposing the photoresist on the semiconductor film portion.

[0011]

Embodiments of the present invention will now be described in detail with reference to the accompanying drawings. 1 to 8 are process diagrams showing an embodiment of a method of manufacturing an active matrix substrate according to the present invention. First, as shown in FIG. 1A, a two-layer structure film made of niobium nitride (NbN) and tantalum (Ta) is formed on a transparent substrate 1 made of glass or the like by a sputtering method or the like, A plurality of scanning signal lines 2 having protruding gate electrodes 2a are formed by lithography.
The niobium nitride (NbN) and tantalum (Ta) are light shielding members. Note that FIG. 1A is a cross-sectional view taken along the line AA in FIG.

Next, as shown in FIG. 2, silicon nitride (S) is formed so as to cover the scanning signal line 2 adjacent to the gate electrode 2a.
iN _x ) film and / or silicon oxide (SiO _x ) film, etc., insulating film 3, semiconductor film 4 made of amorphous silicon film containing no impurities, semiconductor film made of amorphous silicon film containing carbon, nitrogen, etc. 5, a semiconductor film 6 made of a microcrystalline silicon film containing a semiconductor impurity such as phosphorus is sequentially formed by, for example, a plasma CVD method. The semiconductor film 4 made of an amorphous silicon film containing no impurities acts as a channel of the switching transistor, and the semiconductor film 5 made of an amorphous silicon film containing carbon, nitrogen, etc. is selected for etching with the semiconductor film 6. The semiconductor film 6 formed of a microcrystalline silicon film or the like containing a semiconductor impurity such as phosphorus is provided to form an ohmic contact. Silicon nitride (Si
The N _x ) film and / or the silicon oxide (SiO _x ) film is a translucent member. The semiconductor layers 4, 5, 6 also transmit light.

Next, as shown in FIG. 3, the laminated film 3,
The semiconductor film 4 containing no impurities of 4, 5, and 6, the semiconductor film 5 containing carbon or nitrogen, and the microcrystalline semiconductor film 6 containing semiconductor impurities are island-shaped by photolithography so that they remain on the gate electrode 2a. Pattern.
The insulating film 3 is not removed.

Next, as shown in FIG. 4, a transparent conductive film 7 made of ITO or the like is formed on the entire surface by a sputtering method or the like. The transparent conductive film 7 becomes the source / drain electrodes and the pixel electrode of the switching transistor.

Next, as shown in FIG. 5A, the unnecessary portion of the transparent conductive film 7 is photo-processed so that the pixel electrode extending to the scanning signal line 2 adjacent to the source / drain electrodes is formed. Remove by lithography. An additional capacitance is formed by the adjacent scanning signal line 2 and the transparent conductive film 7 on the scanning signal line 2. At this stage, as shown in FIG. 5B, the image signal line has not been formed yet. Note that FIG.
5A is a cross-sectional view taken along the line AA in FIG.

Next, as shown in FIG. 6, in order to divide the source / drain electrodes of the switching transistor,
A negative type photoresist 8 containing, for example, polyisoprene as a main component is applied to the entire surface including the transparent conductive film 7 and exposed from the back surface side of the transparent substrate 1 using the gate electrode 2a as a mask. Each of the laminated films 3, 4, 5, 6, 7 is a scanning signal line 2
Further, since all of them except the gate electrode 2a are light-transmitting members, the photoresist 8 is exposed to light except a portion facing the scanning signal line 2 and the gate electrode 2a. That is, since the source / drain electrode material 7 is a transparent conductive film and the photoresist 8 is a negative type, the photoresist which is self-aligned with the gate electrode 2a as shown in FIG. The pattern 8 can be formed. Further, during the back surface exposure, the photoresist pattern 8 in the portion facing the scanning signal line 2 is not exposed. Therefore, the surface of the transparent substrate 1 is also exposed using a photomask 10 that shields the semiconductor layer 6 portion. As a result, a desired self-alignment pattern can be obtained only in the portions that will be the source / drain electrodes of the switching transistor. That is, in the conventional active matrix substrate, since the light-transmissive member made of molybdenum silicide (MoSi) and aluminum (Al) is used for the source / drain electrodes 7, a photoresist applied on the source / drain electrodes 7 is used. Although the back surface of the substrate 1 cannot be exposed, the back surface of the substrate 1 can also be exposed in the present invention.

Next, as shown in FIG. 7, the transparent conductive film 7 and the microcrystalline semiconductor film 6 containing semiconductor impurities are etched along the photoresist pattern 8 to form the microcrystalline semiconductor layer 6 and the source electrode 7a. And drain electrode 7
Divide b. The drain electrode 7b has a pixel electrode 7c.
Are continuous.

Finally, as shown in FIG. 8, an image signal line 9 is formed by forming a two-layer structure film made of molybdenum silicide (MoSi) and aluminum (Al) by sputtering and patterning.

FIG. 9 is a diagram for explaining another embodiment. In this embodiment, in the step of patterning the transparent conductive film 7 shown in FIG. 5, a portion corresponding to the image signal line 9 portion shown in FIG. 8B is left, and the transparent conductive film 7 in the step shown in FIG. The image signal line 9 is formed at the same time as the patterning. After the image signal line 9 is formed, the exposure step shown in FIG. 6 and the source / drain electrode 7 dividing step shown in FIG. 7 are performed. Therefore, in this embodiment, the image signal line 9 is formed by the process shown in FIG.
The step shown in FIG. 8 is not necessary. Therefore, FIGS.
One process can be omitted as compared with the manufacturing process shown in.

[0020]

As described above, according to the method of manufacturing the active matrix substrate of the present invention, the source / drain is formed from the rear surface side of the transparent substrate on which the plurality of scanning signal lines having the protruding gate electrodes are formed. The photoresist is exposed through the transparent conductive film to be the electrode, and the transparent conductive film in the unexposed portions to be the source / drain electrodes and the semiconductor film to be the ohmic contact layer are removed. There is little overlap in the vertical direction,
The parasitic capacitance between the gate electrode and the drain electrode, which causes flicker and image sticking, can be minimized.

Further, according to the method of manufacturing an active matrix substrate of the present invention, the photoresist is also exposed from the front surface side of the transparent substrate through the photomask which shields the semiconductor film portion from the semiconductor. The photoresist on the scanning signal line can be exposed without exposing the photoresist on the film to light, and the gate electrode can be self-exposed without affecting the pixel electrode extending on the adjacent scanning signal line to form the additional capacitance. The source / drain electrodes can be formed in alignment with each other.

[Brief description of drawings]

FIG. 1 is a process drawing showing an embodiment of a method for manufacturing an active matrix substrate according to the present invention.

FIG. 2 is a process drawing showing an embodiment of the method of manufacturing the active matrix substrate according to the present invention.

FIG. 3 is a process drawing showing an embodiment of the method of manufacturing the active matrix substrate according to the present invention.

FIG. 4 is a process drawing showing an embodiment of the method of manufacturing the active matrix substrate according to the present invention.

FIG. 5 is a process chart showing an embodiment of the method of manufacturing the active matrix substrate according to the present invention.

FIG. 6 is a process drawing showing an embodiment of the method of manufacturing the active matrix substrate according to the present invention.

FIG. 7 is a process chart showing an embodiment of the method of manufacturing the active matrix substrate according to the present invention.

FIG. 8 is a process chart showing an embodiment of the method of manufacturing the active matrix substrate according to the present invention.

FIG. 9 is a diagram showing another embodiment of the method for manufacturing an active matrix substrate according to the present invention.

FIG. 10 is a diagram showing a method of manufacturing a conventional active matrix substrate.

[Explanation of symbols]

1 ... Translucent substrate, 2 ... Scanning signal line, 2a ...
Gate electrode, 3 ... Insulating film, 4, 5, 6 ... Semiconductor film, 7 ... Transparent conductive film, 8 ... Photoresist, 1
0 ... Photo mask

Claims (2)

[Claims] 1. A plurality of scanning signal lines, each of which is composed of a light-shielding member provided with a gate electrode protruding on a transparent substrate,
The scanning signal line is covered with an insulating film made of a translucent member, and a semiconductor film and a transparent conductive film extending from the semiconductor film to an adjacent scanning signal line are formed on the gate electrode portion on the insulating film. Then, after applying a photoresist on the transparent conductive film, from the back surface side of the transparent substrate to the photoresist and from the front surface side of the transparent substrate through a photomask that shields the semiconductor film portion Exposed,
A method for manufacturing an active matrix substrate, wherein a part of the transparent conductive film and a part of the semiconductor film in a non-exposed portion of the photoresist is removed. 2. The image signal line made of a transparent conductive film is formed at the same time when the transparent conductive film extending from the semiconductor film to the adjacent scanning signal line is formed. A method for manufacturing the active matrix substrate described.