JPH0636134B2 - Thin film transistor matrix and method of forming the same - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Outline] In a first aspect of the invention, a gate bus line leading out a gate electrode on a lower layer side has an end portion having substantially the same thickness as the gate electrode and a main portion thicker than the end portion. It consists in forming a staircase.

A second invention is a method of forming the same, wherein a plurality of gate electrodes and a gate bus line connecting the gate electrodes are selectively formed on the surface of the transparent insulating substrate, and a positive photoresist formed on the gate bus line is formed. The film is over-exposed from the backside of the substrate using a self-alignment method using the gate bus line as a mask, and the photoresist film is left on the gate bus line, and anisotropic dry etching is performed using the photoresist film as a mask. Then, a predetermined amount of the surface of the exposed portion of the gate electrode and the gate bus line is removed by a method, and then the photoresist film is removed to form the gate bus line in a stepwise laminated structure.
The gate bus line thus obtained can have a stepwise cross-sectional shape with thin end portions and thicker portions than the gate electrode at other portions.

[Industrial application field]

The present invention relates to a thin film transistor matrix used for driving liquid crystal and the like and a method for forming the same.

[Conventional technology]

A thin film transistor (hereinafter abbreviated as TFT) matrix of a liquid crystal display device obtains a display by driving each TFT through two kinds of intersecting bus lines, and a short circuit is made between these two kinds of bus lines and each TFT. Occurs, not only the pixel of the portion where the short circuit occurs but also the display defect of the entire line including the pixel occurs. Therefore, the short circuit defect between the bus line and the TFT becomes a serious obstacle in the TFT matrix panel.

Fig. 3 shows the structure of a conventional gate and gate bus line.
It is shown in a plan view of (a) and (b) and a sectional view taken along the line BB.

In the figure, 1 is a glass substrate, 2 is a gate bus line, and 3 is a gate electrode.

Conventionally, a metal such as Ti as an electrode material is deposited on the surface of the glass substrate 1 to a thickness of about 80 nm, and the gate bus line 2 and the gate electrode 3 are formed by the photolithographic patterning method and the etching method.

After that, the gate insulating film is formed by the plasma chemical vapor deposition (P-CVD) method. However, satisfactory coverage cannot be obtained in the shoulder portions of the gate bus line 2 and the gate electrode 3, Therefore, problems such as a short circuit defect with a conductive layer such as an address electrode formed in the upper layer and a reduction in breakdown voltage occur in this portion.

Therefore, if the film thickness of the gate electrode 3 is made thin in order to improve the coverage, the film thickness of the gate bus line 2 formed at the same time also becomes thin, so that the resistance of the bus line becomes high and it becomes difficult to drive. Problems arise when it causes trouble.

In order to solve this difficulty, there is also a method of forming the gate bus line 2 and the gate electrode 3 in separate steps, but in this case, the number of photomasks and the steps are increased, so that the yield is reduced and the cost is increased. There is a problem.

[Problems to be solved by the invention]

As described above, in the conventional manufacturing method, there is a problem in the characteristics and reliability of the liquid crystal display device, and an attempt to solve this difficulty requires an additional photomask, which leads to a reduction in yield and an increase in man-hours, resulting in high cost. There was a problem that became.

The present invention eliminates the need for an extra photomask,
An object of the present invention is to provide a thin film transistor matrix capable of preventing the occurrence of short circuit defects and reduction of breakdown voltage, and a method for forming the same.

[Means for solving problems]

In order to achieve the above object, in the first invention,
As shown in the plan views of FIGS. (A) and (b) and the cross-sectional view taken along the line AA, the cross-sectional shape of the gate bus line leading out the gate electrode on the lower layer side is shown in FIG. And an end portion having substantially the same thickness, and a main portion thicker than this end portion.

A second aspect of the invention is a method for forming the same, which is shown in FIGS. 2 (a) to 2 (d) in the order of the manufacturing steps.

Reference numeral 3 is a gate electrode, and 4 is a gate bus line, which are first formed in the same step on the surface of the transparent insulating substrate 1 such as a glass substrate. Then, a photoresist film 5'is formed on the gate bus line 4 by a self-alignment method, and an anisotropic dry etching method is performed using the photoresist film 5'as a mask to expose the gate electrode 3 and the gate bus line 4. The surface of the part is removed by a predetermined amount.

In this way, the end portion 10 of the gate electrode 3 and the gate bus line 2 connected to the gate electrode 3 can be formed thin and the main portion 11 can be formed in a thick step shape, thus improving the coverage at the shoulder portion of the gate electrode 3 and the gate bus line 4. To be done.

[Action]

As shown in FIG. 1, since the gate bus line has a stepped structure, the film thicknesses of the gate electrode 3 and the gate bus line 4 can be selected to desired values. Therefore, the resistance of the bus line 4 can be freely controlled even if the thickness of the gate electrode 3 is reduced. Further, as shown in FIG. 2, since the patterning is performed by the self-alignment method, no new photomask is required, and this work is precise and easy.

〔Example〕

An embodiment of the present invention will be described below with reference to FIGS. 1 and 2.

FIGS. 2 (a) to 2 (d) are views sequentially showing the manufacturing process of one embodiment of the present invention, in which the surface of the glass substrate 1 is made of titanium (T
i) is selectively deposited by using, for example, a vapor deposition method to form a gate electrode 3 and a gate bus line 4 connecting the gate electrode 3 and the gate electrode 3.

Next, as shown in FIG. 2B, a positive photoresist film 5 is formed on the entire surface, and exposure is performed from the back surface of the glass substrate 1 as shown by the arrow. At this time, overexposure is performed until all the photoresist film 5 on the gate (width of about 5 μm) 3 is exposed. By doing so, the photoresist film 5 has an unexposed portion 5 ′ on the gate bus line 4.

Then, as shown in FIG. 3C, the photoresist film 5 is developed to leave only the unexposed portion 5'and all other portions are removed to remove the gate bus line 4 '.
And the entire surface of the gate electrode 3 is exposed. Therefore, using this photoresist film 5'as a mask, carbon tetrachloride (CC
using l ₄₎ as an etchant, under a pressure of approximately 10Pascal, by adding approximately 300W RF power of 27.56MHz, anisotropically etching approximately 5 minutes.
As a result, the exposed parts of the gate electrode 3 and the gate bus line 4 are removed by about 40 nm.

Then, by removing the photoresist film 5 ', as shown in FIG. 3D, the end 10 of the gate electrode 3 and the gate bus line 4 connected thereto is approximately 40 nm, and the main portion of the gate bus line 4 is 11 is formed in a step shape with a thickness of approximately 80 nm.

After that, the TFT matrix is completed by proceeding according to the usual manufacturing process.

In the manufacturing process of the TFT matrix obtained in this manner as described above, as shown in FIG. 2 (b), by overexposing from the back surface of the glass substrate 1, the gate electrode 3 is entirely exposed. However, there is an unexposed portion on the gate bus line 4, and this portion remains as a photoresist film 5 '. By using this as a mask, anisotropic dry etching is performed on the gate bus line 4 and the gate electrode 3 to form the gate electrode 3 to a desired thin film thickness as shown in FIG. Has a thick film thickness in the main portion 11 which constitutes the majority, and the end portion 10 connected to the gate electrode 3 for leading out the gate electrode 3.
Can have a thin stepped structure, and the film thicknesses of the gate electrode 3 and the gate bus line 4 can be selected as desired.

Moreover, since the backside exposure process is performed by the self-alignment method using the gate bus line 4 as a mask, it is not necessary to prepare a new photomask, and the work is accurate and extremely simple.

〔The invention's effect〕

According to the present invention, by adding a simple process, the thickness of the gate electrode is made thin, and the gate bus line is formed in a step-like shape having a thin end portion which also serves as a connection portion with the gate electrode and other portions being thick. Therefore, it is possible to obtain a TFT matrix panel which can be made to have a satisfactory conductivity, moreover, the coverage at both shoulders is improved, and short-circuit defects with the conductive layer such as the upper address electrode are few and the withstand voltage is high. To be

[Brief description of drawings]

FIGS. 1 (a) and 1 (b) are views showing a main structure of a TFT matrix according to an embodiment of the present invention, and FIGS. 2 (a) to (d) show a manufacturing process of a forming method according to an embodiment of the present invention. FIG. 3A and FIG. 3B are cross-sectional views of a main part showing the structure of the main part for explaining the problems of the conventional TFT matrix. In the figure, 1 is a glass substrate, 2 and 4 are gate bus lines, 3 is a gate electrode, 5 and 5'are photoresist films,
Reference numeral 10 indicates an end portion, and 11 indicates a main portion.

Claims (2)

[Claims] 1. A display active matrix panel in which transistor elements corresponding to pixels are arranged in a matrix, and a gate electrode (3) and a drain electrode of each element are led out through bus lines in the row and column directions. The gate bus line (4) for leading out the gate electrode (3) has a step shape composed of an end portion (10) having substantially the same thickness as the gate electrode and a main portion (11) thicker than the end portion. A thin film transistor matrix characterized by the above. 2. A lower layer gate in a display active matrix panel in which pixel-corresponding transistor elements are arranged in a matrix, and a gate electrode (3) and a drain electrode of each element are led out through row and column direction bus lines. When forming electrodes and gate bus lines, a gate electrode (3) and a gate bus line connected to the gate electrode (3) by selectively depositing a predetermined conductive material on the surface of the transparent insulating substrate (1) Forming a positive photoresist film (5) on the surface of the transparent insulating substrate (1) including the gate electrode (3) and the gate bus line (4), and The photoresist film (5) is overexposed from the back surface of the transparent insulating substrate (1) using (3) and the gate bus line (4) as a mask to form the gate. A step of leaving a photoresist film (5 ') narrower than the gate bus line (4) on the line (4), and an anisotropic dry etching method using the photoresist film (5') as a mask, A thin film transistor comprising: a step of removing a predetermined amount of the surface of the gate electrode (3) and an exposed surface of the gate bus line (4); and a step of removing the photoresist film (5 '). Method of forming matrix.