JP2759207B2 - Method of forming pixel electrode and thin film transistor - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a pixel electrode in which a transparent pixel electrode and a staggered thin film transistor for driving the pixel electrode are formed on a transparent substrate used for a liquid crystal display device. And a method of forming a thin film transistor.

[Conventional technology]

An inverted staggered thin film transistor is used as a thin film transistor for driving a pixel electrode provided on a pixel electrode forming substrate of an active matrix type liquid crystal display element in correspondence with each pixel electrode. The thin film transistor of the above, on a gate electrode formed on the substrate surface, a gate insulating film, a channel layer made of ia-S1 semiconductor, a contact layer of source and drain made of n ⁺ -a-Si semiconductor, Since the source electrode and the drain electrode are stacked, there is a step between the pixel electrode formation surface (generally, the gate insulating film surface) and the source electrode connecting the pixel electrode. There is a problem that a pixel electrode formed from the surface to the source electrode may be disconnected at the step.

For this reason, recently, it is considered that the pixel electrode is formed on the substrate surface by forming the thin film transistor for driving the pixel electrode into a staggered thin film transistor, and the thin film transistor is formed on the pixel electrode.

FIG. 8 shows a conventional method for forming a pixel electrode and a thin film transistor when forming a pixel electrode on a substrate surface and forming a staggered thin film transistor on the pixel electrode in the order of steps. The thin film transistor is formed as follows.

First, as shown in FIG. 8 (a), a substrate (glass substrate) 1
A transparent conductive film 2 such as ITO serving as a pixel electrode is applied to almost the entire surface, a resist mask A1 is formed thereon, and the transparent conductive film 2 is etched. As shown in FIG. 2B, patterning is performed in the shape of the pixel electrode a. Next, as shown in FIG. 8 (c), the first metal film 3 serving as the source and drain electrodes of the thin film transistor and the source and drain are formed over substantially the entire surface of the substrate 1 on which the pixel electrode a is formed. After sequentially stacking a first semiconductor film (n ⁺ -a-Si film) 4 serving as a contact layer, a resist mask A2 is formed thereon, and the semiconductor film 4 and the metal film 3 are etched. 4 and the metal film 3 are formed into the shapes of a source electrode S whose outer portion overlaps the pixel electrode a, a drain electrode D, and a data line (not shown) connected thereto, as shown in FIG. 8 (d). Perform patterning. Next, as shown in FIG. 8 (e), a second semiconductor film (ia-Si film) 5 serving as a channel layer of the thin film transistor is formed over substantially the entire surface of the substrate 1.
, A gate insulating film 6 of SiN or the like, and a second
Metal film 7 is sequentially laminated, and a resist mask A3 is formed thereon.
Is formed and etching is performed to pattern this laminated film (the second metal film 7, the insulating film 6, and the second semiconductor film 5) into the shape of the gate electrode G and control lines (not shown) connected thereto. Then, a staggered thin film transistor T as shown in FIG. 8 (f) is formed, and at this time, an unnecessary portion of the first semiconductor film 4 serving as a contact layer between the source and the drain (below the gate electrode G). The portion excluding the transistor element region) is also etched away. Thereafter, as shown in FIG. 8 (g), a protective insulating film 8 of polyimide or the like is applied to almost the entire surface of the substrate 1 on which the pixel electrode a and the thin film transistor T are formed, and a resist mask is formed thereon. A4 is formed, and this protective insulating film 8 is patterned by an etching method so as to cover the transistor element region, the data line and the control line as shown in FIG. 8 (h). In FIG. 8H, reference numeral 9 denotes an alignment film formed on the surface of the substrate 1 after forming the pixel electrode a and the thin film transistor T as described above.

[Problems to be solved by the invention]

However, according to the above-described conventional method of forming a pixel electrode and a thin film transistor, first, a transparent conductive film 2 is applied to the surface of the substrate 1 and the transparent conductive film 2 is patterned to form a pixel electrode a. In addition, since the thin film transistor T is formed by the above-described steps, the number of steps is large, which hinders mass production and cost reduction.

The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a method for forming a pixel electrode and a thin film transistor, which can form a pixel electrode and a staggered thin film transistor in a small number of steps. Is to provide.

[Means for solving the problem]

A transparent conductive film, a first metal film, and a contact layer are sequentially laminated on substantially the entire surface of the substrate to form a first laminated film, and a side wall of the transparent conductive film and the first metal film are formed. The first stacked film is patterned into a shape of a pixel electrode, a drain electrode, and a data line such that a side wall and a side wall of the contact layer are exposed and the side walls substantially overlap the substrate surface. A first patterning step, a semiconductor film containing the same kind of material as the contact layer, a gate insulating film, and a second metal film are sequentially laminated on the first laminated film to form a second laminated film. Forming, patterning the second laminated film into the shape of a gate electrode, and removing the contact layer while leaving the contact layer overlapping the patterned semiconductor layer; An insulating film is coated on the second metal film and the first metal film and the insulating film so that the first metal film of the data line is left and a part of the transparent conductive film is exposed. A third patterning step of patterning; and an alignment film forming step of forming an alignment film on the exposed transparent conductive film.

[Operation] That is, according to the present invention, since the pixel electrode and the source electrode and the drain electrode of the thin film transistor are formed at the same time, compared with the conventional method in which the pixel electrode and the thin film transistor are formed in separate steps. As a result, the number of steps can be reduced, so that mass production and cost reduction can be achieved.

〔Example〕

Hereinafter, a first embodiment of the present invention will be described with reference to FIGS.

First, as shown in FIG. 1 (a), a substrate (glass substrate) 1
A transparent conductive film 2 such as ITO serving as a pixel electrode is deposited on the entire surface to a thickness of 500 mm by sputtering or the like, and then a first conductive film 2 made of Cr or the like serving as source and drain electrodes of a thin film transistor is formed thereon. Metal film 3 is deposited to a thickness of 500.degree. By a sputtering method or a vacuum evaporation method, and a first semiconductor film (n.sup. ⁺ -A-Si film) serving as a contact layer with a source and a drain is further formed thereon. 4 is deposited to a thickness of 250 ° by a plasma CVD method or the like. Next, a resist mask B1 is formed on the first laminated film laminated on the surface of the substrate 1, and the semiconductor film 4, the metal film 3, and the transparent conductive film 2 of the first laminated film are sequentially dry-etched. The first laminated film is formed by etching the first laminated film into a pixel electrode a and a shape of a source electrode S continuous with the pixel electrode a and a drain electrode D and a drain electrode D, as shown in FIGS. 1 (b) and 2. Is patterned into the shape of the data line Da leading to. At this time, the pixel electrode a and the source electrode S, the drain electrode D, and the data line Da are laminated films of the transparent conductive film 2, the first metal film 3, and the first semiconductor film 4, The pixel electrode a and the data line Da
Finally, a single-layer film composed of only the transparent conductive film 2 is obtained.
Next, after the resist mask B1 is peeled off, as shown in FIG. 1 (c), the second semiconductor film (ia-Si film) to be a channel layer of the thin film transistor is formed on almost the entire surface of the substrate 1. 5) 500 by plasma CVD method etc.
A gate insulating film 6 such as SiN.
Is deposited to a thickness of 400 mm by a plasma CVD method or the like, and a second metal film 7 such as Al serving as a gate electrode of a thin film transistor is further formed thereon to a thickness of 2000 mm by a sputtering method or a vacuum evaporation method. Second to adhere
Is formed. Next, a resist mask B2 is formed on the second laminated film, and the metal film 7 of the second laminated film is formed.
, The gate insulating film 6 and the semiconductor film 5 are sequentially etched by a dry etching method, so that the second
As shown in FIG. 1 (d) and FIGS. 3 and 4, the gate electrode G and the control line Ga connected thereto are patterned to form a thin film transistor T,
Subsequent to the patterning of the second laminated film, the first semiconductor film 4 and the first metal film 3 on the pixel electrode a formed by patterning the transparent conductive film 2 are sequentially removed by etching. Then, the pixel electrode a is exposed. At this time,
The first semiconductor film 4 and the first metal film 3 in the data line Da portion exposed by the patterning of the second stacked film are also etched, so that the source electrode S and the drain electrode D
Are left as a two-layer film composed of the transparent conductive film 2 and the metal film 3, respectively, but the data line Da is a single-layer film composed of only the transparent conductive film 2. Thereafter, as shown in FIG. 1 (e),
Substrate 1 on which pixel electrode a and thin film transistor T are formed
A protective insulating film 8 made of polyimide or the like is applied to almost the entire surface, and a resist mask B3 is formed thereon,
This protective insulating film 8 is patterned by dry etching so as to cover the transistor element region, the data line Da and the control line Ga as shown in FIG. 1 (f), and thereafter, an alignment film 9 is formed on the surface of the substrate 1. I do.

That is, the method of forming the pixel electrode and the thin film transistor is such that a transparent conductive film 2 serving as a pixel electrode, a first metal film 3 serving as source and drain electrodes,
By sequentially laminating a first semiconductor film 4 serving as a contact layer with the drain and patterning the first laminated film, the pixel electrode a and the source electrode S continuous thereto, the drain electrode D and the data Line Da is formed at the same time, and then the second semiconductor film 5 serving as a channel layer is formed.
, A gate insulating film 6, and a second metal film 7 serving as a gate electrode are sequentially stacked, and the second stacked film is patterned to form a channel layer, a gate insulating film 6,
The gate electrode G is formed at the same time, and the first semiconductor film 4 and the first metal film 3 on the pixel electrode a are removed to expose the pixel electrode a during the patterning of the second laminated film. According to this method, since the pixel electrode a and the source electrode S and the drain electrode D of the thin film transistor T are formed at the same time, the etching for patterning the deposited film on the surface of the substrate 1 requires: The etching of the first stacked film shown in FIG. 1A and the etching of the first stacked film and the first semiconductor film 4 and the first metal film 3 shown in FIG. Only three times of etching of the protective insulating film 8 shown in FIG. 1 (e) are required, and therefore, compared with the conventional method in which the pixel electrode and the thin film transistor are formed in separate processes (four etching steps). To reduce the number of processes Since the kill, it is possible to measure the mass production and cost reduction.

In the first embodiment, at the time of patterning the second laminated film, the first semiconductor film 4 and the first metal film 3 of the data line Da exposed by the patterning of the second laminated film are also etched. Therefore, the data line Da becomes a single-layer film including only the transparent conductive film 2. However, according to the second embodiment described below, the data line Da is formed by the transparent conductive film 2 and the metal film 3. Can reduce the resistance of the data line Da.

5 to 7 show a second embodiment of the present invention. In this embodiment, a pixel electrode and a thin film transistor are formed as follows.

First, as shown in FIGS. 5A to 5C, a transparent conductive film 2 serving as a pixel electrode, a source and a drain are formed on the surface of the substrate 1 in the same manner as in the first embodiment described above. A first metal film 3 serving as an electrode and a first semiconductor film 4 serving as a contact layer between a source and a drain are sequentially laminated, and the first laminated film is formed as a pixel electrode a and a source electrode connected thereto. S
After patterning into the shape of the drain electrode D and the shape of the data line Da, the second semiconductor film 5 serving as a channel layer, the gate insulating film 6 and the second The second metal film 7 is sequentially stacked to form a second stacked film. Next, a resist mask B2 is formed on the second laminated film, and the metal film 7, the gate insulating film 6, and the semiconductor film 5 of the second laminated film are sequentially etched to form the second laminated film. As shown in FIGS. 5 (d), 6 and 7, the film is
And forming a thin film transistor T by patterning into the shape of the control line Ga connected thereto, and following the patterning of the second laminated film, the transparent conductive film 2
The first semiconductor film 4 on the pixel electrode a formed by patterning is etched and removed until the first metal film 3 thereunder is exposed. Complete the data line Da consisting of two layers. At this point, the first metal film 3 also remains on the pixel electrode a. Next, as shown in FIG. 5 (e), a protective insulating film 8 of polyimide or the like is applied to almost the entire surface of the substrate 1 on which the pixel electrode a and the thin film transistor T are formed, and a resist mask B3 is formed thereon. Is formed, and the protective insulating film 8 is patterned into a shape covering the transistor element region, the data line Da and the control line Ga as shown in FIG. 1 (f). The metal film 3 is removed by etching to expose the pixel electrode a, and thereafter, the alignment film 9 is formed on the surface of the substrate 1.

Thus, also in the second embodiment, the pixel electrode a
And the source electrode S and the drain electrode D of the thin film transistor T are formed at the same time, so that the etching for patterning the deposited film on the surface of the substrate 1 is performed by etching the first laminated film shown in FIG. The etching, the etching of the first laminated film and the first semiconductor film 4 shown in FIG. 5C, and the i-th etching on the protective insulating film 8 and the pixel electrode a shown in FIG. Only three times of etching with the metal film 3 of
Therefore, as in the first embodiment, mass production and cost reduction can be achieved by reducing the number of steps, and according to this embodiment, the first semiconductor film is patterned at the time of patterning the second laminated film. Only the first metal film 3 on the pixel electrode a is removed by patterning the second laminated film while leaving only the first metal film 3 by etching only 4 so that the pixel electrode a is exposed. Therefore, the resistance of the data line Da can be reduced by using the data line Da as a two-layer film of the transparent conductive film 2 and the metal film 3.

〔The invention's effect〕

According to the method for forming a pixel electrode and a thin film transistor of the present invention, the pixel electrode and the source electrode and the drain electrode of the thin film transistor can be formed at the same time, so that the pixel electrode and the thin film transistor are formed in separate steps. Since the number of steps can be reduced as compared with the method (1), mass production and cost reduction can be achieved.

[Brief description of the drawings]

1 to 4 show a first embodiment of the present invention. FIG. 1 is a view showing a process of forming a pixel electrode and a thin film transistor, FIG. 2 is a plan view of FIG. FIG. 3 is a plan view of FIG. 1 (d), and FIG. 4 is a sectional view taken along line IV-IV of FIG. 5 to 7 show a second embodiment of the present invention. FIG. 5 is a view showing a process of forming a pixel electrode and a thin film transistor, FIG. 6 is a plan view of FIG. FIG. 7 is a sectional view taken along the line VII-VII of FIG. FIG. 8 is a process chart for forming a conventional pixel electrode and thin film transistor. DESCRIPTION OF SYMBOLS 1 ... Substrate, 2 ... Transparent conductive film, a ... Pixel electrode, 3 ... First metal film, S ... Source electrode, D ... Drain electrode, Da ... Data line, 4 ... First semiconductor film, 5 ... Second Semiconductor film,
6 gate insulating film, 7 second metal film, G gate electrode, Ga control line, T thin film transistor, 8 protective insulating film, 9 alignment film, B1, B2, B3 resist mask.

Claims (1)

(57) [Claims] A transparent conductive film is provided on almost the entire surface of a substrate.
A first stacked film is formed by sequentially stacking a first metal film and a contact layer, and a side wall of the transparent conductive film, a side wall of the first metal film, and a side wall of the contact layer are exposed; A first patterning step of patterning the first laminated film into a shape of a pixel electrode, a drain electrode, and a data line such that these side walls substantially overlap the substrate surface; A semiconductor film containing the same kind of material as the contact layer, a gate insulating film, and a second metal film are sequentially stacked thereon to form a second stacked film, and the second stacked film is used as a gate electrode. A second patterning step of patterning into a shape and removing the contact layer while leaving the contact layer overlapping the patterned semiconductor layer; and coating an insulating film on the first metal film and the second metal film. A third patterning step of patterning the first metal film and the insulating film so as to leave the first metal film of the data line and expose a part of the transparent conductive film; A method for forming a pixel electrode and a thin film transistor, comprising: an alignment film forming step of forming an alignment film thereon.