JP3281167B2 - Method for manufacturing thin film transistor - 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 of manufacturing a thin film transistor, and more particularly, to a method of manufacturing a thin film transistor used for driving a liquid crystal of a liquid crystal display device. 2. Description of the Related Art In recent years, thin film transistor (TFT) matrix type color liquid crystal panels used for laptop personal computers and wall-mounted televisions have been developed and commercialized. T
It has been recognized that FT matrix type color liquid crystal panels can be substituted for CRTs in terms of display quality.
Further improvements in price, reliability, manufacturing yield, and the like are desired.

[0002]

2. Description of the Related Art As one of measures for improving the reliability and manufacturing yield of a TFT matrix type color liquid crystal panel,
Further improvements in TFT matrices are desired. FIG.
(A), (b) to FIG. 10 are sectional views for explaining a method of manufacturing a TFT matrix used for a TFT matrix type color liquid crystal panel.

FIG. 9A shows a state after an interlayer insulating film is formed by covering each electrode and before a via hole for connecting these electrodes to a pixel electrode or the like is formed. In the drawing, particularly, a drain terminal portion, a pixel portion, and a gate terminal portion are shown. In the pixel section, a gate electrode 2 and a lower electrode 3 of an auxiliary capacitor are formed on a transparent substrate 1, and a gate insulating film 5 is formed to cover these electrodes 2 and 3. Further, a TFT is formed above the gate electrode 2 with a gate insulating film 5 interposed therebetween, and the TFT has source / drain electrodes 6a and 6b whose uppermost layer is an Al film. Above the lower electrode 3, an upper electrode 7 of an auxiliary capacitor whose uppermost layer is an Al film is formed via a gate insulating film 5. Further, an interlayer insulating film 9 is formed to cover the source / drain electrodes 6a and 6b and the upper electrode 7.

In the drain terminal portion, a drain terminal 8 having an uppermost layer formed of an Al film is formed on a transparent substrate 1 via a gate insulating film 5, and the drain terminal 8 is formed by an interlayer insulating film 9. Coated. Further, in the gate terminal portion, a gate terminal 4 composed of two conductive films of Ti and Al films on the transparent substrate 1 and a gate insulating film 5 covering the gate terminal 4.
And an interlayer insulating film 9 are formed.

Then, as shown in FIG. 9B, through an etching process based on a resist mask, an interlayer insulating film 9 on the drain terminal 8 and an interlayer insulating film 9 on the source electrode 6a in the pixel portion are formed. Openings 10a, 10b, 10c and 10d are formed in the interlayer insulating film 9 on the upper electrode 7 and in the gate insulating film 5 and the interlayer insulating film 9 on the gate terminal 4, respectively. Opening 10
The Al films are exposed at the bottoms of a to 10d, respectively.

[0006] Next, as shown in FIG.
After forming a transparent conductive film so as to cover ~ 10d, it is patterned and connected to the source electrode 6a and the upper electrode 7 of the pixel portion to form the pixel electrode 11b, and connected to the drain terminal 8 and the gate terminal 4. Lead electrodes 11a, 11c
To form Thereby, the TFT is completed.

[0007]

In the above-described method of manufacturing a TFT, an Al film is formed to overlap the electrodes and the wiring layers connected to the electrodes in order to reduce the resistance. But A
The openings 10a to 10d are formed in the interlayer insulating film 9 and the like on the film l, and the pixel electrode 11b and the lead electrode 11 are formed through the openings 10a to 10d.
When a and 11c are formed, it is difficult to make contact between the pixel electrode 11b and the like and the Al film, and in some cases, the contact resistance varies and increases. This is probably because a natural oxide film was formed on the surface of the Al film, or an etching residue was re-adhered to the surface of the Al film during etching for forming the openings 10a to 10d.

For this reason, when the TFT is operated to drive the liquid crystal, the voltage applied to the liquid crystal layer varies or decreases depending on the pixel due to the uneven contact resistance, and a uniform color tone cannot be obtained. In the case of halftone display, a display defect may be caused due to a point defect or the like. The present invention
It was created in view of the problems of the conventional example, and A
It is an object of the present invention to provide a method of manufacturing a thin film transistor which can suppress a variation in contact resistance between an l film and a transparent conductive film and keep the contact resistance small.

[0009]

The first object of the present invention is to provide a thin film transistor formed on a transparent substrate, the first being a source / drain electrode, wherein at least the uppermost conductive film is an Al film. Forming an insulating film by covering the drain electrode, forming an opening in the insulating film on the source / drain electrode, and etching the Al film in the opening through the opening; Forming a transparent conductive film in contact with the source / drain electrodes in the opening, wherein the source / drain electrodes are refractory metal films under the Al film. The thin film transistor according to the first aspect of the present invention, wherein the underlying high-melting metal film is exposed by etching the Al film. Be achieved by law, the third, performed by wet etching the etching of the Al film,
Then, the insulating film on the side wall of the opening is side-etched, the opening of the insulating film is widened, and the side wall surface of the insulating film in the opening is aligned with the side wall surface of the Al film in the opening. Fourth, a fourth method of manufacturing a thin film transistor according to the second invention, wherein the upper electrode of the auxiliary capacitor formed on the transparent substrate, wherein at least the upper two conductive films are formed of Al in order from the upper layer. Applying the steps for the source / drain electrodes simultaneously to the upper electrode which is a film and a refractory metal film, and connecting the upper electrode and the source / drain electrodes by the transparent conductive film. A fifth aspect of the present invention is achieved by the method of manufacturing a thin film transistor according to the second or third aspect, wherein the etching of the Al film is etching of a surface layer of the Al film. Is achieved by the manufacturing method of thin film transistor according to the first aspect, wherein the sixth
A step of forming a conductive film by covering the opening after the step of forming an opening in the insulating film, and continuously etching the conductive film and a surface layer of the Al film in the opening. Seventh, after the step of forming an insulating film by covering the source / drain electrodes, the etching-resistant film used as a mask for forming the opening is left. Etching a surface layer of the Al film in the opening through the opening, forming a conductive film covering the opening,
A first step of removing the etching-resistant film and leaving the conductive film in the opening; and a step of forming a transparent conductive film in contact with the conductive film in the opening. Eighth, with respect to the upper electrode of the auxiliary capacitor formed on the transparent substrate, wherein at least the uppermost conductive film is an Al film, The thin film transistor according to the fifth, sixth, or seventh invention, wherein the steps for the source / drain electrodes are simultaneously applied, and the upper electrode and the source / drain electrodes are connected by the transparent conductive film. Achieved by the manufacturing method of
Ninth, the thin film transistor according to the first, second, third, fourth, fifth, sixth, seventh or eighth invention, wherein the transparent conductive film is an ITO film or a ZnO film Is achieved.

[0010]

According to the method of manufacturing a thin film transistor of the present invention, before connecting the transparent conductive film to the source / drain electrodes of the TFT in which the upper two layers of the conductive film are the Al film and the refractory metal film in this order from the upper layer. Then, the uppermost Al film is removed,
The refractory metal film underlying the Al film is exposed.

It has been experimentally confirmed that a high-melting-point metal film can provide better contact with a transparent conductive film than an Al film. Therefore, the etching residue such as an insulator is removed from the surface of the source electrode and the like, and the transparent conductive film, for example, the ITO film or the ZnO film can be connected to the high melting point metal film having good contact properties.

By the way, when the Al film is etched, the Al film may be wet-etched in order to obtain a selectivity with respect to the refractory metal film. In this case, since the Al film is side-etched by the wet etching of the Al film, A step occurs in the opening. Also in this case, after the wet etching of the Al film, the insulating film on the side wall of the opening is side-etched to widen the opening width of the insulating film so that the side wall surface of the insulating film in the opening and the side wall surface of the Al film in the opening are aligned. Therefore, the step in the opening is eliminated. Therefore, the risk of disconnection of the transparent conductive film formed by covering the opening is reduced, and the reliability and the manufacturing yield can be improved.

Further, a TFT in which the uppermost layer is an Al film
Before connecting the source / drain electrodes and the transparent conductive film, the surface layer of the Al film is removed, or after the conductive film is formed, the conductive film and the surface layer of the Al film are continuously removed, or the surface layer of the Al film is removed. After the removal, a conductive film is formed. Therefore, an etching residue such as an insulator or a natural oxide film is removed from the surface of the Al film, or a conductive film,
For example, Mo, Ti, T having good contact with the transparent conductive film
Since the a, Cr film or the ITO film is exposed, the contact between the transparent conductive film and the source / drain electrodes is improved.

Thus, it is possible to suppress the variation in the contact resistance between the transparent conductive film and the source / drain electrodes, and keep the contact resistance small.

[0015]

【Example】

(1) First Embodiment of the Present Invention FIG. 3 is a plan view showing the entire structure after a TFT matrix is formed on a transparent substrate of a liquid crystal display panel. FIG.
As shown in FIG. 2, a plurality of pixels having the same configuration are arranged in a matrix in the vertical and horizontal directions on a transparent glass substrate. Here, one pixel and a gate terminal and a drain terminal connected thereto will be described.

In FIG. 3, reference numeral 37b denotes a pixel electrode made of an ITO film (transparent conductive film). The pixel electrode 37b is connected to the source electrode via two openings 36b on the source electrode (source / drain electrodes) of the TFT. I do. Reference numeral 23 denotes a gate bus line connected to the gate electrode of the TFT, and the gate electrode of the TFT of each pixel arranged in the vertical direction in the drawing is connected to each other. A gate terminal 24 is connected to the gate bus line 23. One gate bus line 23 and the like are connected to each gate terminal 24 and the like.

Reference numeral 38 denotes TF via a drain electrode of the TFT.
The drain electrodes of the TFTs of the pixels arranged in the horizontal direction in the drawing are connected to drain drain lines connected to T, respectively. A drain terminal 32 is connected to the drain bus line 38. One drain bus line 38 and the like are connected to each drain terminal 32 and the like. Reference numeral 34 denotes an upper electrode of an auxiliary capacitor formed at the same time as the drain terminal 32 on the glass substrate with the same material as the drain terminal 32, the source electrode 33a, and the drain electrode 33b via the gate insulating film. 23 are formed in parallel.

A lower electrode is formed below the upper electrode 34 with a storage capacitor insulating film interposed therebetween. A region where the upper electrode 34 and the lower electrode overlap each other is the upper electrode 34 / the storage capacitor insulating film / the lower electrode. Functions as a capacitor consisting of electrodes. The upper electrode 34 is connected to the pixel electrode 37b through two openings 36c and the like. The pixel electrode 37b and a common electrode (not shown) opposed to each other via a liquid crystal layer (not shown) constitute a parasitic capacitor composed of the pixel electrode 37b / liquid crystal layer / common electrode. Therefore, the capacitor of the storage capacitor insulating film is connected in parallel with the capacitor of the liquid crystal layer with the common source electrode 33a. This compensates for a decrease in the capacitance of the capacitor of the liquid crystal layer having the voltage dependency, and suppresses a color shift or the like due to a change in the voltage applied to the liquid crystal layer.

Next, a method of manufacturing the TFT matrix of FIG. 3 according to the first embodiment of the present invention will be described with reference to FIG.
This will be described with reference to FIGS. 2 (a) and 2 (b) and FIGS. 2 (a) and 2 (b). In each drawing, a drain terminal portion, a pixel portion, and a gate terminal portion are shown from the left. The drain terminal is AA in FIG.
The TFT portion of the pixel portion corresponds to the cross-sectional view taken along the line BB of FIG. 3, the storage capacitor portion of the pixel portion corresponds to the cross-sectional view taken along the line CC of FIG. 3, and the gate terminal portion corresponds to the cross-sectional view of FIG. This corresponds to a cross-sectional view taken along line DD of FIG.

As shown in FIG. 1A, a gate electrode 22, a gate bus line 23 connected to the gate electrode 22, and a gate connected to the gate bus line 23 are formed on a transparent glass substrate (transparent substrate) 21. The terminal 24 and the lower electrode 25 of the storage capacitor are formed. Of these, the gate electrode 22
Is composed of a Ti film, and all others are composed of a two-layered conductive film of a Ti film and an Al film covering the Ti film.

Subsequently, a silicon nitride film 26 having a thickness of about 4000.degree. Is formed by plasma CVD so as to cover the gate electrode 22, the gate bus line 23, the gate terminal 24 and the lower electrode 25. The silicon nitride film 26 on the gate electrode 22 becomes a gate insulating film, and the silicon nitride film 26 on the lower electrode 25 becomes an auxiliary capacitance insulating film. Then, about film thickness
150-500 シ リ コ ン amorphous silicon film (a-Si film;
(Operation semiconductor layer) 27 and a silicon nitride film having a thickness of about 1200 ° are continuously formed by a plasma CVD method.

Next, after a resist film (not shown) is formed by a spin coating method, the resist film is selectively exposed using an exposure mask.
Develop to form a gate electrode 22 above the gate electrode 22
A narrower island-shaped resist film is left. Next, the silicon nitride film is etched and removed by reactive ion etching (RIE) using a chlorine-based or fluorine-based reaction gas using the resist film as a mask to form a channel protection film 28. The silicon nitride film may be removed by wet etching using a buffered hydrofluoric acid solution (BHF).

Next, on the channel protective film 28 and the a-Si film 27, an n ⁺ a-Si
After the film 29 is formed, the film thickness is approximately 800
Then, an Al film 31 having a thickness of about 500 ° is formed on the Ti film 30 by an evaporation method or the like. Next, the Al film 31 and the T film are formed by reactive ion etching (RIE) using a chlorine-based or fluorine-based reaction gas, using a newly formed resist film (not shown) as a mask.
The i film 30, the n ⁺ a-Si film 29, and the a-Si film 27 are continuously etched and removed.

As a result, the active semiconductor layer 27a of the transistor comprising the a-Si film 27 and the n ⁺ a-Si film 29 / Ti film 30 / Al film 31 connected to the active semiconductor layer 27a
A source electrode 33a and a drain electrode 33b made of
A drain bus line composed of a Si film 27 / n ⁺ a-Si film 29 / Ti film 30 / Al film 31;
A drain terminal 32 on which the n ⁺ a-Si film 29 / Ti film 30 / Al film 31 are laminated is formed.

Next, the drain terminal 32, the drain bus line, the TFT, and the upper electrode 34 of the auxiliary capacitor are covered, and a silicon nitride film (insulating film) 35 having a thickness of about 2000.degree. I do. Next, as shown in FIG. 1B, the silicon nitride film 35 is selectively etched and removed by dry etching using SF ₆ based on a resist mask (not shown) to remove the drain terminal 32 and the source of the TFT. Openings 36a to 36c are formed in the silicon nitride film 35 on the electrode 33a and the upper electrode 34, and openings 36d are formed in the gate insulating film 26 and the silicon nitride film 35 on the gate terminal 24. As a result, the opening 36
An Al film 31 appears at the bottom of a to 36c, and an Al film of the gate terminal 24 appears at the bottom of the opening 36d. However, an etching residue may remain on the surface of the Al film, and an oxide film may be naturally formed on the surface of the Al film when left in the air.

If an ITO film is formed as it is, there is a risk that the contact becomes insufficient.
As shown in FIG. 2A, the bottom Al film is etched through the openings 36a to 36d. Thereby, the openings 36a to 36c
The Ti film 30 is exposed at the bottom of the gate electrode 24, and the Ti film of the gate terminal 24 appears at the bottom of the opening 36d. At this time, as the etching of the Al film, dry etching using a chlorine-based reaction gas or wet etching using heated phosphoric acid is used.

Next, an ITO film having a thickness of about 800.
An nO film (transparent conductive film) is formed by a sputtering method. Next, as shown in FIG. 2B, after forming a resist mask (not shown), the ITO film or the ZnO film is selectively etched based on the resist mask, and the drain terminal is formed through the openings 36a to 36d. Drain extraction electrode connected to 32
37a, a pixel electrode 37b connected to the source electrode 33a and the upper electrode 34, and a gate lead electrode 37c connected to the gate terminal 24 are formed.

As described above, according to the method of manufacturing a TFT matrix according to the first embodiment of the present invention, as shown in FIG. Drain terminal 32, TFT source electrode 33a,
Before the upper electrode 34 and the gate terminal 24 are connected to the ITO film, the Al film 31 and the like are removed to expose the underlying Ti film 30 and the like such as the Al film 31.

The Ti film 30 and the like have a higher I
It has been experimentally confirmed that good contact can be obtained with the TO films 37a to 37c. Accordingly, the etching residue such as an insulator is removed from the surface of the source electrode 33a and the like, and the ITO films 37a to 37c can be connected to the Ti film 30 and the like having good contact properties.

Thus, the variation in the contact resistance is suppressed, the contact resistance is kept small, the voltage is uniformly applied to the liquid crystal layer over the entire pixel, and the color tone modulation and the point defect are prevented from occurring. Can be. Therefore, reliability and manufacturing yield can be improved. (2) Second Embodiment of the Present Invention A second embodiment of the present invention will be described with reference to FIGS. Hereinafter, only the pixel portion will be described, and the other portions will not be described because they are the same.

The opening 36 of the first embodiment shown in FIG.
In the step of etching and removing the Al film 31 and the like via a to 36d, in the dry etching, the Al film 31 and the like and the underlying Ti film 30 and the like such as the Al film 31 have almost no etching selectivity. It becomes difficult to detect the end point of the etching of the film 31 or the like. Therefore, especially when the danger of over-etching is high and the influence is large,
In order to etch the Al film 31, wet etching may be performed with heated phosphoric acid.

In this case, as shown in FIG.
Side etching of the film 31 occurs, and the Al film 31 is removed wider than the widths of the openings 36b and 36c of the interlayer insulating film 35, and the opening
From the side walls of the interlayer insulating film 35 in 36b and 36c, the interlayer insulating film 3
5, the end side wall of the Al film 31 recedes. Therefore, since a step is generated in this portion, when the ITO film is formed so as to cover the openings 36b and 36c, disconnection of the ITO film easily occurs in the step.

In order to avoid this danger, in the second embodiment, as shown in FIG. 4B, after etching the Al film 31 through the openings 36b and 36c by wet etching, CF ₄ + O ₂ The interlayer insulating film 35 is etched by a chemical dry etching (CDE) method using a gas. As a result, the interlayer insulating film 35 on the side walls in the openings 36b and 36c undergoes side etching to widen the opening width. After an appropriate etching time, the interlayer insulating film 35 has already receded below the interlayer insulating film 35 in the openings 36e and 36f. Al film 31
And the side wall surface of the interlayer insulating film 35 coincides.

For example, when the Al film 31 having a thickness of 500 ° is over-etched about 1.5 times as much as the just etching, the side etching amount is about 0.5 μm on one side. At this time, by performing CDE at 300 W for about 30 seconds, the side wall of the interlayer insulating film 35 recedes by about 0.5 μm on one side, and the side wall surface of the end portion of the Al film 31 and the side wall surface of the interlayer insulating film 35 substantially coincide with each other. Become like

Therefore, according to the second embodiment, the opening 36
The risk of disconnection of the ITO film formed by covering e and 36f is reduced, and the reliability and the production yield can be improved. (3) Third to Fifth Embodiments of the Present Invention Third to fifth embodiments of the present invention will be described with reference to FIGS. In the third to fifth embodiments, instead of removing the entire Al film as in the first and second embodiments,
Only the surface layer of the Al film is etched. There are the following three methods. Hereinafter, only the pixel portion will be described, and the drain terminal portion and the gate terminal portion will not be described because they are the same.

(A) Third Embodiment FIGS. 5A to 5D are sectional views showing a third embodiment. The openings 36b and 36 of the first embodiment shown in FIG.
After the step of forming c, as shown in FIG.
The resist film at the time of forming the layers 36b and 36c is removed, and thereafter, as shown in FIG. 5B, the Al film 31 is formed through the openings 36b and 36c by dry etching using Ar ions.
Is etched by about 20 to 200 °.

Next, as shown in FIG. 5C, an ITO film is formed again on the entire surface and then patterned to form a pixel electrode (transparent conductive film) 37b. In the above steps,
The etching of the surface layer of the Al film 31 and the formation of the ITO film 37b are preferably performed continuously under reduced pressure. This can prevent a natural oxide film from being formed again on the surface of the Al film after the etching, so that good contact between the ITO film 37b and the Al film 31 can be obtained.

(B) Fourth Embodiment FIGS. 6A to 6C are sectional views showing a fourth embodiment. The openings 36b and 36 of the first embodiment shown in FIG.
After the step of forming c, as shown in FIG.
The resist film at the time of forming the layers 36b and 36c is removed, and thereafter, as shown in FIG. 6B, an ITO film (conductive film) 41 is formed on the entire surface.

Subsequently, as shown in FIG.
The entire film 41 and the surface layer of the Al film 31 of about 50 to 70 ° are wet-etched. By doing this,
A which is difficult to remove only by processing the Al film 31 alone
The natural oxide film on the surface of the 1 film 31 can be removed. Next, as shown in FIG.
After forming the O film, patterning is performed to form a pixel electrode (transparent conductive film) 37b.

(C) Fifth Embodiment FIGS. 7A to 7C and FIGS. 8A and 8B are cross-sectional views showing a fifth embodiment.

The opening 36 of the first embodiment shown in FIG.
After the step of forming the openings 36b and 36c, as shown in FIG. 7A, the resist film (etching-resistant film) 42 when the openings 36b and 36c are formed is left as it is in FIG.
As shown in (b), the solution containing phosphoric acid is used to form the Al film 3.
1 is wet-etched by about 20 to 200 °. Next, as shown in FIG. 7C, a Mo film, T
Conductive film 43 made of i film, Ta film, Cr film or ITO film
To form

Next, as shown in FIG. 8A, the resist film 42 is removed. At this time, only the conductive film 43 on the resist film 42 is removed by lift-off, and the openings 36b,
Mo film, Ti film, Ta film, Cr formed in 36c
Only the conductive films 43a and 43b made of films or ITO films remain. Next, as shown in FIG. 8B, an ITO film is formed again on the entire surface and then patterned to form a pixel electrode 37b. At this time, since the ITO film (transparent conductive film) 37b in the openings 36b and 36c is formed on the conductive films 43a and 43b, a good contact can be obtained.

As described above, according to the manufacturing method of the thin film transistor matrix of the third to fifth embodiments of the present invention,
The source electrode 33 of the TFT in which the uppermost layer is the Al film 31
Before connecting the upper film 34a and the upper electrode 34 of the storage capacitor to the ITO film 37b, the surface layer of the Al film 31 is removed or the Al film 3 is removed.
After removing the surface layer of No. 1, conductive films 43a and 43b made of Mo film, Ti film, Ta film, Cr film or ITO film are formed.

Accordingly, after the etching residue such as an insulator or the natural oxide film is removed from the surface of the source electrode 33a or the like, or after the conductive film 41 is formed on the Al film 31,
And the surface layer of the Al film 31 is continuously removed, or
The O film 37b is a film having good contact properties, a Ti film, a Ta film, and a C film.
Since it is connected to the conductive films 43a and 43b made of the r film or the ITO film, the electrical connectivity between the ITO film 37b and the source electrode 33a is improved.

Thus, the ITO film 37b and the source electrode 33
It is possible to suppress the variation of the contact resistance during the period a and the like and keep the contact resistance small. For this reason, when the TFT is operated, it is possible to prevent a voltage from being uniformly applied to the liquid crystal layer over the entire pixel, thereby preventing color tone modulation and point defects. Therefore, the reliability and manufacturing yield of the liquid crystal display device can be improved.

In the first to fifth embodiments, the ITO films 37a to 37c are used as the transparent electrodes.
A membrane can also be used. Also in this case, the ITO film 37a
An effect similar to that of 37c can be obtained. Also, the Al film 3
Although the Ti film 30 is used as the refractory metal film below the substrate 1, a Ta film, a Mo film, or the like may be used.

[0047]

As described above, in the method of manufacturing a thin film transistor matrix according to the present invention, the upper two conductive films are an Al film and a refractory metal film in order from the upper layer.
Before connecting the source / drain electrodes of the FT and the ITO film, the uppermost Al film is removed to expose the underlying refractory metal film.

Therefore, the etching residue such as an insulator is removed from the surface of the source electrode and the like, and the transparent conductive film can be connected to the high melting point metal film having good contact properties. After the wet etching of the Al film, the insulating film on the side wall of the opening is side-etched to widen the opening width of the insulating film so that the side wall surface of the insulating film in the opening and the side wall surface of the Al film in the opening are aligned. Therefore, the step in the opening caused by the wet etching of the Al film is eliminated. Therefore, the risk of disconnection of the transparent conductive film formed by covering the opening is reduced, and the reliability and the manufacturing yield can be improved.

Further, a TFT in which the uppermost layer is an Al film
Before connecting the source / drain electrodes to the transparent conductive film, the surface layer of the Al film is removed, or the conductive film is formed after removing the surface layer of the Al film. Therefore, etching residues such as insulators and natural oxide films are removed from the surface of the Al film,
Alternatively, a conductive film, for example, a Mo, Ti, Ta, Cr film or an ITO film having good contact with the transparent conductive film is exposed on the contact surface with the transparent conductive film. The contact between them is improved.

Thus, the variation in the contact resistance between the transparent conductive film and the source / drain electrodes can be suppressed, and the contact resistance can be kept low. For this reason, when the TFT is operated, it is possible to prevent a voltage from being uniformly applied to the liquid crystal layer over the entire pixel, thereby preventing color tone modulation and point defects. Therefore, the reliability and manufacturing yield of the liquid crystal display device can be improved.

[Brief description of the drawings]

FIG. 1 is a sectional view (part 1) illustrating a method for manufacturing a thin film transistor matrix according to a first embodiment of the present invention.

FIG. 2 is a sectional view (part 2) illustrating the method for manufacturing the thin film transistor matrix according to the first embodiment of the present invention.

FIG. 3 is a plan view showing a configuration of a thin film transistor matrix according to an example of the present invention.

FIG. 4 is a sectional view illustrating a method for manufacturing a thin film transistor matrix according to a second embodiment of the present invention.

FIG. 5 is a sectional view illustrating a method for manufacturing a thin film transistor matrix according to a third embodiment of the present invention.

FIG. 6 is a sectional view illustrating a method for manufacturing a thin film transistor matrix according to a fourth embodiment of the present invention.

FIG. 7 is a sectional view (part 1) illustrating a method for manufacturing a thin film transistor matrix according to a fifth embodiment of the present invention.

FIG. 8 is a sectional view (part 2) illustrating the method for manufacturing the thin-film transistor matrix according to the fifth embodiment of the present invention.

FIG. 9 is a cross-sectional view (part 1) illustrating a method for manufacturing a thin film transistor matrix according to a conventional example.

FIG. 10 is a sectional view (part 2) illustrating the method for manufacturing the thin-film transistor matrix according to the conventional example.

[Explanation of symbols]

Reference Signs List 21 glass substrate (transparent substrate), 22 gate electrode, 23 gate bus line, 24 gate terminal, 25 lower electrode, 26 gate insulating film, 27 a-Si layer (operating semiconductor layer), 28 protective insulating film, 29 n ⁺ a -Si layer, 30Ti film (high melting point metal film), 31Al film, 32 drain terminal, 33a source electrode, 33b drain electrode, 34 upper electrode, 35 silicon nitride film (insulating film), 36a to 36f opening, 37a drain Lead electrode, 37b Pixel electrode (ITO film; transparent conductive film), 37c Gate lead electrode, 38 Drain bus line, 41 ITO film (conductive film), 42 Resist film (etching resistant film), 43, 43a, 43b Conductive film .

Continued on the front page (72) Inventor Hidetoshi Ishiwari 1015 Uedanaka, Nakahara-ku, Kawasaki City, Kanagawa Prefecture Inside Fujitsu Co., Ltd. Person Atsushi Inoue 1015 Uedanaka, Nakahara-ku, Kawasaki City, Kanagawa Prefecture Inside Fujitsu Limited (72) Inventor Shiro Hirota 1015, Kamiodanaka, Nakahara-ku, Kawasaki City, Kanagawa Prefecture Inside Fujitsu Limited (56) References JP 5-323373 ( JP, A) JP-A-4-253342 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) H01L 29/786 H01L 21/28 H01L 21/336 G02F 1/1368

Claims (9)

(57) [Claims] 1. A step of forming an insulating film by covering source / drain electrodes of a thin film transistor formed on a transparent substrate, wherein the source / drain electrodes at least the uppermost conductive film is an Al film Forming an opening in the insulating film on the source / drain electrode; etching the Al film in the opening through the opening; contacting the source / drain electrode in the opening Forming a transparent conductive film. 2. The source / drain electrode has a refractory metal film formed below the Al film, and the underlying refractory metal film is exposed by etching the Al film. A method for manufacturing a thin film transistor according to claim 1. 3. The etching of the Al film is performed by wet etching, and thereafter, the insulating film on the side wall of the opening is side-etched, and the opening of the insulating film is widened to form a side wall surface of the insulating film in the opening. And Al in the opening
3. The method of manufacturing a thin film transistor according to claim 2, wherein the side wall surface of the thin film is aligned with the film. 4. An upper electrode of an auxiliary capacitor formed on the transparent substrate, wherein at least the upper two conductive films are an Al film and a refractory metal film in order from the upper layer. 4. The method according to claim 2, wherein the steps for the source / drain electrodes are simultaneously applied, and the upper electrode and the source / drain electrodes are connected by the transparent conductive film. . 5. The method according to claim 1, wherein the etching of the Al film is etching of a surface layer of the Al film. 6. A step of forming an opening in the insulating film, forming a conductive film covering the opening, and continuously etching the conductive film and a surface layer of the Al film in the opening. The method for manufacturing a thin film transistor according to claim 1. 7. After the step of forming an insulating film by covering the source / drain electrodes, leaving the etching-resistant film used as a mask for forming the opening through the opening in the opening. Said A
etching a surface layer of the film, forming a conductive film by covering the opening, and subsequently removing the etching-resistant film to leave the conductive film in the opening; Forming a transparent conductive film in contact with the conductive film. 8. The method according to claim 1, wherein the upper electrode of the storage capacitor formed on the transparent substrate and the upper electrode having at least the uppermost conductive film is an Al film is formed on the source / drain electrode. 8. The method of manufacturing a thin film transistor according to claim 5, wherein the upper electrode and the source / drain electrodes are connected by the transparent conductive film. 9. The method according to claim 1, wherein the transparent conductive film is an ITO film or a ZnO film. A method for manufacturing a thin film transistor according to claim 8.