JPH0812357B2 - Method for manufacturing TFT substrate - Google Patents

Description

The present invention relates to a method for manufacturing a liquid crystal display panel, and more particularly to an improvement in a method for manufacturing a TFT substrate for a liquid crystal display panel.

[Prior Art] FIG. 2A shows a TF for a liquid crystal display panel in a conventional manufacturing method.
FIG. 2B is a plan view schematically showing a part of the T substrate, and FIG.
2B is a sectional view taken along the line 2B-2B in FIG.

With reference to these figures, first, a Ta layer is deposited on a glass substrate 11 by sputtering and patterned to form a gate electrode line 1. The surface layer of the gate electrode line 1 is anodized to form the first gate insulating film 2 made of Ta ₂ O ₅ .

Next, the SiN _X layer 3 to be the second gate insulating film, the a-Si semiconductor layer 4 to be the channel layer of the TFT, and the SiN _X layer 5 to be the etch stopper film are sequentially deposited on the entire surface by the plasma CVD method. Deposit. The SiN _X layer 5 is patterned to have a width smaller than that of the gate electrode line 1,
It becomes the etch stopper film 5.

After that, an n ⁺ -a-Si layer for enabling ohmic contact with the a-Si layer 4 is deposited on the entire surface, and this is patterned at the same time as the a-Si layer 4 to form the TFT channel layer 4 and source. A contact layer 6a and a drain contact layer 6b are formed. At this time, the etch stopper film 5 is a
-It serves to prevent the channel portion of the Si layer 4 from being etched.

Next, a Ti layer is deposited on the entire surface by sputtering and patterned to form a source electrode line 7a and a drain electrode 7b.

Further, a transparent ITO (indium tin oxide) layer is deposited on the entire surface by sputtering, and this is patterned to form a pixel electrode 8. In the figure, the TFT
Are enlarged in comparison with the pixel electrode 8 for clarity.

Finally, the SiN _X protective film 1 is formed on the entire surface by the plasma CVD method.
2 is formed. At this time, all the source electrode lines 7a and all the gate electrode lines 1 are electrically short-circuited by the short-circuit ring to prevent charge-up during plasma CVD.
Then, after the liquid crystal cells are bonded together, the short-circuit ring is opened.

[Problems to be Solved by the Invention] In the conventional manufacturing method as described above, plasma CV is used.
All the source electrode lines 7a and all the gate electrode lines 1 are short-circuited by the short-circuit ring when the SiN _X protective film 12 is formed by the D method, but each pixel electrode 8 is electrically separated from these electrode lines 7a, 1. Has been done. Therefore, each pixel electrode is
It is easy to be charged by the influence of ions and radicals during D. When a certain pixel electrode is significantly charged up, the characteristic of the TFT connected to it is that the threshold voltage V _TH
Fluctuations.

FIG. 3 is a graph showing such variations in threshold voltage. Here, V _G represents the gate voltage, and I _D represents the drain current. That is, a normal TFT is as shown by the solid curve. The characteristics of the TFT, which has characteristics but was connected to the charged-up pixel electrode, tends to shift in the negative direction of V _G as shown by the dotted curve. This means that the threshold voltage V _TH becomes lower. A TFT having such a low threshold voltage is not in a sufficiently OFF state with a normal gate voltage, which causes a point defect in the display during display.

In view of the above problems of the prior art, it is an object of the present invention to provide a method for manufacturing a TFT substrate that does not cause fluctuations in the threshold voltage of a TFT during formation of a protective film by plasma CVD.

[Means for Solving the Problems] According to the present invention, a TFT, a first electrode line connected to one conduction end of the TFT, a pixel electrode connected to the other conduction end of the TFT, and a TFT are controlled. The method for manufacturing a TFT substrate for a liquid crystal display panel, which has gate electrode lines for protection and is covered with a protective film, is such that the pixel electrode is short-circuited to the first electrode line before the protective film is formed, and protection is performed by the plasma CVD method. The step of opening a short circuit between the pixel electrode and the first electrode line after forming the film is included.

[Operation] According to the manufacturing method of the present invention, since the pixel electrode is short-circuited with the first electrode line when the protective film is formed by the plasma CVD method, the pixel electrode is not charged up. Therefore, the threshold voltage of the TFT is not changed during the formation of the protective film.

[Example] FIG. 1A shows a TF for a liquid crystal display panel according to the manufacturing method of the present invention.
FIG. 1B is a plan view schematically showing a part of the T substrate, and FIG.
FIG. 1B is a sectional view taken along the line 1B-1B in FIG.

With reference to these figures, first, a Ta layer is deposited on a glass substrate 11 by sputtering and patterned to form a gate electrode line 1. The surface of the gate electrode line 1 is anodized to form a first gate insulating film 2 made of Ta ₂ O ₅ .

Next, the SiN _X layer 3 to be the second gate insulating film, the a-Si semiconductor layer 4 to be the channel layer of the TFT, and the SiN _X layer 5 to be the etch stopper film are sequentially deposited on the entire surface by the plasma CVD method. Deposit. The SiN _X layer 5 is patterned to have a width smaller than that of the gate electrode line 1,
It becomes the etch stopper film 5.

After that, an n ⁺ -a-Si layer for enabling ohmic contact with the a-Si layer 4 is deposited on the entire surface, and this is patterned at the same time as the a-Si layer 4 to form the TFT channel layer 4 and source. A contact layer 6a and a drain contact layer 6b are formed. At this time, the etch stopper film 5 is a
-It serves to prevent the channel portion of the Si layer 4 from being etched.

Next, a Ti layer is deposited on the entire surface by sputtering, and this is patterned to form a source electrode line 7a and a drain electrode line 7b.

Further, a transparent ITO layer is deposited on the entire surface by sputtering, and this is patterned to form a pixel electrode 8. In this case, the picture element electrode 8 has a protrusion 9,
It is formed by short-circuiting with the source electrode line 7a.

After that, the SiN _x protective film 12 is formed on the entire surface by the plasma CVD method. At this time, all the source electrode lines 7a and all the gate electrode lines 1 are electrically short-circuited by the short-circuit ring to prevent charge-up during plasma CVD. By the way, since the pixel electrode 8 is also short-circuited to the source electrode line 7a via the protrusion 9, the charge-up of the pixel electrode 8 is also prevented.

Finally, a through hole 10 is opened in the protective film 12, and the projection 9 of the pixel electrode 8 is etched through the through hole. As a result, the pixel electrode 8 becomes the source electrode line 7a.
Electrically separated from. Further, the short-circuit ring between all the source electrode lines 7a and all the gate electrode lines 1 is opened after the liquid crystal cells are bonded together.

In the manufacturing process according to the present invention as described above,
Compared with the conventional process, there is no increase in the number of steps in the thin film forming process and the aligner process, and only one step is added in the etching process.

[Effects of the Invention] As described above, according to the present invention, it is possible to provide a method for manufacturing a TFT substrate that does not cause fluctuations in the threshold voltage of the TFT during the formation of the protective film by plasma CVD.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1A is a TFT for a liquid crystal display panel manufactured by the manufacturing method of the present invention.
It is a top view which shows a part of board | substrate schematically. FIG. 1B is a sectional view taken along the line 1B-1B in FIG. 1A. FIG. 2A is a plan view schematically showing a part of a TFT substrate manufactured by a conventional manufacturing method. FIG. 2B is a sectional view taken along line 2B-2B in FIG. 2A. FIG. 3 is a graph showing variations in TFT characteristics. In the figure, 1 is a Ta gate electrode line, 2 is a Ta ₂ O ₅ anodic oxide film, 3 is a SiN _X gate insulating film, 4 is an a-Si semiconductor layer, and 5 is
SiN _X etch stopper film, 6a and 6b are n ⁺ -a-Si contact layers, 7a and 7b are Ti source electrode lines and drain electrodes, 8 is an ITO pixel electrode, 9 is a projection of the pixel electrode, 10 is a through hole portion of the protective film 12, 11 is a glass substrate,
12 indicates a protective film. In the drawings, the same reference numerals indicate the same contents or corresponding parts.

Continuation of the front page (51) Int.Cl. ⁶ Identification number Reference number within the agency FI Technical indication location H01L 27/12 K 29/786 (72) Inventor Hiroshi Hamada 22-22 Nagaike-cho, Abeno-ku, Osaka-shi, Osaka Prefecture Sharp Incorporated (56) References JP 62-84563 (JP, A) JP 64-48035 (JP, A)

Claims (1)

[Claims] 1. A TFT (thin film transistor), a first electrode line connected to a source electrode of the TFT, a pixel electrode connected to a drain electrode of the TFT, and a gate electrode connected to a gate electrode of the TFT. In a method of manufacturing a TFT substrate having lines, which are covered with a protective film, the pixel electrode is short-circuited to the first electrode line at a position other than the TFT formation region before the protective film is formed. Then, after forming the protective film by a plasma CVD (chemical vapor deposition) method, a short circuit between the pixel electrode and the first electrode line is opened, and a manufacturing method of a TFT substrate.