JP3197003B2 - Liquid crystal display panel and method of manufacturing the same - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a liquid crystal display panel, and more particularly, to a liquid crystal display in which an indium tin oxide (hereinafter referred to as ITO) film used for a charge retaining capacitor portion, a pixel portion, and a wiring portion is crystallized. About the panel.

[0002]

2. Description of the Related Art In recent years, an active matrix type liquid crystal display panel has been receiving attention as a display unit for a flat display device. The prior art of this type of liquid crystal display panel will be described with reference to the drawings.

FIG. 5 is a cross-sectional view showing the structure of a conventional liquid crystal display panel. In FIG. 5, reference numeral 501 denotes a transparent substrate, 502 denotes a polycrystalline silicon film, 503 denotes a gate oxide film, 504 denotes a gate electrode, 505 denotes a source / drain region, 505 denotes a common extraction lower electrode, 507 denotes a common electrode, and 508 denotes an interlayer. Insulating films, 509 and 510 are through holes, 511 are source / drain electrodes, 512 is a common lead electrode, 513 is a pixel electrode, 514 is a switching TFT section, 515 is a charge retaining capacitor section, 51
Reference numeral 6 denotes a common electrode lead portion.

The prior art shown in FIG. 5 shows the structure of one pixel of an active matrix liquid crystal display panel. One pixel is composed of a switching TFT section 514, a charge holding capacitor section 515, and a common electrode lead. Part 51
6.

The switching TFT section 514 is connected to a source / drain region 505 made of a polycrystalline silicon film doped with an impurity and to a source / drain region 505 via a contact hole 509 provided in an interlayer insulating film 508. Source / drain electrode 51 made of Al
1 and a gate oxide film 50 on the polycrystalline silicon film 502.
3 and a gate electrode 504 provided through the gate electrode 504.

The charge holding capacitor 515 is made of ITO.
A common electrode 507 also serving as a lower electrode of a charge holding capacitor made of a film is provided opposite to the common electrode 507 via an interlayer insulating film 508, and is made of an ITO film connected to one of the source / drain electrodes 511. And a pixel electrode 513. Common electrode 507 and pixel electrode 5
13 is a charge holding capacitor composed of TF
This is to obtain a display with good image quality by compensating for deterioration of display images and display unevenness caused by a change over time of T off current and a decrease in liquid crystal resistance.

The common electrode extraction portion 516 is connected to the common extraction lower electrode 5 connected to the common electrode 507.
06 and through holes 510 provided in the interlayer insulating film 508.
And a common extraction electrode 512 made of Al and connected to the common extraction lower electrode 506 through the common electrode.

In the conventional technique configured as described above, the common electrode lead-out portion 516 selectively removes the interlayer insulating film 508 on the common lead-out lower electrode 506 by photo-etching to remove the through-hole 510. The common lower electrode 506 and the common extraction electrode are connected through the through hole 510. For this reason, in this conventional technique, it is necessary to form the lower electrode 506 for extracting the common made of Al, and the number of manufacturing steps is increased accordingly. On the other hand, a structure in which the common extraction electrode 512 is directly connected to the common electrode 507 without the common extraction lower electrode 506 is also conceivable. However, since the ITO film forming the common electrode 507 has no resistance to the hydrofluoric acid-based etchant, the interlayer insulating film 50 on the common electrode 507 is not used.
8 is to be selectively removed by photo-etching to form a through-hole,
It is inevitable that the common electrode 507 by the O film is damaged, and it is difficult to form a through hole.

Therefore, a structure of a liquid crystal panel having a structure in which a through hole is formed on a common electrode made of an ITO film and directly connected to the common lead electrode as described above has not been realized.

As a prior art relating to this type of liquid crystal display panel, for example, a technique described in Japanese Patent Application Laid-Open No. 58-130561 is known.
234756 and Japanese Patent Application No. 63-19657.

[0011]

The prior art described above is
This method requires a lower electrode for common extraction and requires an extra manufacturing process. In addition, a through hole is formed on the common electrode made of an ITO film to directly connect the common electrode and the common extraction electrode. If a connection structure is to be realized, it is unavoidable that the ITO film serving as the common electrode is damaged by etching during the formation of the through-hole, and the yield at the time of manufacturing is reduced, which is not feasible. Was.

An object of the present invention is to solve the above-mentioned problems of the prior art, and to selectively pattern an interlayer insulating film on a common electrode to form a through hole without damaging an ITO film serving as a common electrode. Another object of the present invention is to provide a liquid crystal display panel having a structure in which a common electrode and a common extraction electrode are directly connected. Another object of the present invention is to provide a liquid crystal display panel using a polycrystalline ITO film as a protective film against a hydrofluoric acid-based etchant, utilizing the fact that the polycrystalline ITO film has excellent etching resistance. .

[0013]

According to the present invention, it is an object of the present invention to provide a liquid crystal display panel, wherein a plurality of electrodes made of metal are formed on a substrate of the liquid crystal display panel. An insulating film is formed thereon, and a polycrystalline ITO film having a cubic-byxbite type crystal structure for protecting the plurality of electrodes against a hydrofluoric acid-based etchant is formed on the insulating film. This is achieved by:

The term cubic bixbite means that the cubic is a cubic lattice, and that the bixbite is a modified type of the fluorite type structure. It is a modified oxidized crystal having a fluorite structure having a cubic lattice, and is known as a crystal structure of indium tin.

Hereinafter, the etching resistance of the polycrystalline ITO film to the etchant will be specifically described.

FIG. 2 shows experimental data on the etching resistance of the polycrystalline ITO film found by the present inventors. The polycrystalline ITO film has an amorphous ITO film and a polycrystalline ITO film having a cubic-byxbite type crystal structure. , and is a diagram for explaining the case where the etching S _i O ₂ film which is commonly used for an interlayer insulating film, a PSG film with hydrofluoric acid Etsuchiyanto, the relationship between the etching thickness for etching time.

In FIG. 2, the ITO film is formed by a spatter method.
PSG film and S _i O ₂ film is formed respectively in the atmospheric pressure CVD method, a hydrofluoric acid-based Etsuchiyanto, NH ₄ F and CH ₃ CO
Mixed solution of ₂ H was used.

As is clear from FIG. 2, the amorphous ITO
Film, PSG film, and S _i O ₂ film, little difference in resistance to etching resistance to hydrofluoric acid Etsuchiyanto, amorphous ITO film, PSG film, compared to the interlayer insulating film such as S _i O ₂ film, Poor etching resistance. Therefore, as mentioned above, ITO
When a through hole is formed on a common electrode made of a film, damage to the common electrode is inevitable.

Meanwhile, from FIG. 2, a polycrystalline ITO film having a crystal structure of cubic bixbyite an amorphous ITO film, PSG film, S _i O ₂ film 0.5μm~0.2μ
It can be seen that there is almost no loss in film thickness due to the etching during the m-etching. Therefore, by using a polycrystalline ITO film having a cubic six-byte type crystal structure for the common electrode, it is possible to form a through-hole on the common electrode without damaging the common electrode, thereby achieving the object described above. can do.

The hydrofluoric acid-based etchant includes not only a hydrofluoric acid-based aqueous solution but also CF ₄ , CF ₄ + H ₂ , C ₂ F ₆ , and C ₃ F.
_A hydrofluoric acid-based etching gas composed of ₈ or the like may be used, and the same result as in FIG. 2 was obtained. In addition, as a method of forming the interlayer insulating film, a plasma CVD method, a sputter method, or the like can be used in addition to the normal pressure or reduced pressure CVD method. is there.

Since the polycrystalline ITO film having the above-mentioned structure is excellent in etching resistance, there is a problem in a method of processing the electrode shape. However, after processing the electrode shape in the state of the amorphous ITO film,
The amorphous ITO film can be formed by converting the amorphous ITO film into a polycrystalline ITO film having the above-described structure by performing heat treatment, laser irradiation, or the like. Thereby, the problem of the electrode shape processing method can be solved, and a polycrystalline ITO film can be easily formed.

The changes in the crystallinity and crystal structure of the ITO film are described in the Annual Report of the Faculty of Engineering, The University of Tokyo, Vol. 46, pp. 189-192, and Thin Soiled Films, 151 (198).
7), p.215-p.222 and p.355-p.364.

Since the common electrode is formed of a polycrystalline ITO film having a cubic-byxbite type crystal structure having excellent etching resistance to a hydrofluoric acid-based etchant, the common electrode may be damaged during the etching. Absent. Therefore, according to the present invention, the through-hole is formed by selectively patterning the interlayer insulating film on the electrode without requiring an extra step such as forming a lower electrode for common extraction made of Al or the like. Thus, the common electrode and the common extraction electrode can be directly connected. Further, the polycrystalline ITO film having the above structure has higher transmittance and electric conductivity, is superior in characteristics as a transparent conductive film, and improves characteristics as a liquid crystal display panel, as compared with an amorphous ITO film. Further, by utilizing the etching resistance of the polycrystalline ITO film, the polycrystalline ITO film can be used as a protective film against a hydrofluoric acid-based etchant.

[0024]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The structure of a liquid crystal display panel according to an embodiment of the present invention and a method of manufacturing the same will be described in detail with reference to the drawings.

FIGS. 1 (a) to 1 (f) are views showing cross sections of a pixel and a common electrode lead-out portion of a liquid crystal display panel according to the present invention for each manufacturing process. In FIG. 1, 10
1 is a glass substrate, 102 is a polycrystalline silicon film, 103 is a gate oxide film, 104 is a gate electrode, and 105 is a source electrode.
Drain electrodes, 106 and 106 'are common electrodes, 107
Is an interlayer insulating film, 108 and 109 are through holes, 110
Is a source / drain electrode, 111 is a common extraction electrode, 112 is a pixel electrode, 113 is a switching TFT
Reference numeral 114 denotes a charge holding capacitor part, and 115 denotes a common electrode lead-out part.

As shown in FIG. 1F, one pixel and the common electrode lead-out portion of the liquid crystal display panel according to the present invention are constituted by a switching TFT portion 113, a charge holding capacitor portion 114, and a common electrode lead-out portion 115. The common electrode lead-out portion 115 is directly connected to the common lead-out electrode 111 through a through hole 109 provided on the common electrode 106 serving as a lower electrode of the capacitor. In that it is formed of a polycrystalline ITO film,
The configuration is different from that of the prior art described with reference to FIG.

Hereinafter, the manufacturing method will be described with reference to FIGS. 1 (a) to 1 (f).

(1) First, a CV is placed on a glass substrate 101.
A polycrystalline silicon film 102 is formed by the method D, and is processed into an island shape by photo-etching (FIG. 1A).

(2) Next, the gate oxide film 103 and the gate electrode 104 are respectively formed by the CVD method, and after the electrode shapes of the gate oxide film 103 and the gate electrode 104 are formed by photo-etching, ion implantation is performed. A portion of the polycrystalline silicon film 102 which is not covered with the gate oxide film 103 is doped with an impurity by diffusion or the like to form a source / drain region 105. Next, the amorphous I
After the TO film is formed on the entire surface, the charge holding capacitor portion 1 is formed.
A common electrode shape 106 'also serving as the lower electrode 14 is formed by photoetching (FIG. 1B).

(3) Next, the amorphous ITO film forming the common electrode 106 'also serving as the lower electrode is subjected to a heat treatment at a temperature of 200 ° C. or more, for example, to form a cubic film.
It is converted into a common electrode 106 of a polycrystalline ITO film having a bixbite type crystal structure [FIG. 1 (c)].

(4) Next, as the interlayer insulating film 107,
S _i O ₂ film or PSG film 107 formed by CVD
Is formed on the entire surface, and then a photo-fluoric acid-based etchant is used.
By etching, through holes 108 and 109 for contact are formed on the source / drain region 105 and the common electrode lead-out portion 115. At this time, since the common electrode 106 has been converted to a polycrystalline ITO film having a cubic-byxbite type crystal structure having excellent etching resistance to a hydrofluoric acid-based etchant, the common electrode 106 is not damaged without being damaged. The through-hole 109 can be formed by selectively removing the upper interlayer insulating film 107 [FIG. 1D].

(5) Next, the through holes 108 and 1
A source / drain electrode 110 and a common extraction electrode 111 are formed on the substrate 09 [FIG. 1 (e)].

(6) Finally, a pixel electrode 112 made of an ITO film is formed [FIG. 1 (f)].

In the above-described embodiment of the present invention, the common electrode is a polycrystalline ITO film, and a through-hole is provided on the common electrode to form a common extraction electrode. In the case of selectively patterning the insulating film of (1), by converting the ITO film to a polycrystalline ITO film having a cubic-byxbite type crystal structure having excellent etching resistance to hydrofluoric acid-based etchant, It can be applied to other cases.

Further, if attention is paid to the etching resistance of a polycrystalline ITO film having a cubic-byxbite type crystal structure, this polycrystalline ITO film can be used as a protective film against a hydrofluoric acid-based etchant.

FIGS. 3 and 4 (a) to 4 (c) are cross-sectional views showing the structure of another embodiment of the present invention using a polycrystalline ITO film as a protective film. In FIG. 3 and FIG.
Reference numerals 118 indicate protection films made of an ITO film, and other reference numerals are the same as those in FIG.

In the embodiment shown in FIG. 3, when the pixel electrode 112 is formed in the manufacturing process described with reference to FIG. 1F, not only the pixel electrode 112 but also the switching TFT section 113, the source / drain electrode 110, A protective film 116 made of an ITO film is also formed on the Al wiring such as the common extraction electrode 111, and thereafter, a heat treatment is applied.
The pixel electrode 112 and the protective film 116 made of ITO are converted into a polycrystalline ITO film having a cubic-byxbite type crystal structure, and the other portions are configured in the same manner as the embodiment described with reference to FIG. I have.

In the embodiment of the present invention shown in FIG. 3 configured as described above, since the Al wiring is protected by the polycrystalline ITO film having the cubic bixbite type crystal structure, the polycrystalline silicon TFT is formed. In a later manufacturing process, even when the substrate is exposed to a hydrofluoric acid-based etchant atmosphere, for example, when a cleaning process is performed, damage to the Al wiring can be prevented.

The embodiment shown in FIGS. 4A to 4C is an example in which a protective film made of ITO is provided on another portion.

FIG. 4A shows a cross section of a cross portion of a gate wiring and a source / drain wiring of a polycrystalline silicon TFT portion in the embodiment of the present invention described with reference to FIG.

As described above, the source / drain electrodes 110
When exposed to a hydrofluoric acid-based etchant and a cleaning solution while the gate electrode 104 and the gate electrode 104 are insulated only by the interlayer insulating film 107, the thickness of the interlayer insulating film 107 is reduced or a pinhole defect is generated. May occur.

FIGS. 4 (b) and 4 (c) show a multi-layered structure having a cubic-byxbite type crystal structure in order to prevent the above-described decrease in the thickness of the interlayer insulating film 107 and the generation of pinhole defects. An example is shown in which a crystalline ITO film is selectively formed in a cross wiring portion and used as a protective film in the cross wiring portion. In the example shown in FIG.
A protective film 117 made of a film is provided on the upper part of the interlayer insulating film 107. In the example shown in FIG.
A protective film 118 made of a TO film is provided inside the interlayer insulating film 117. In each of the examples shown in FIGS. 4 (b) and 4 (c), it is possible to protect the wiring or the cross section of the electrode by etching.

Further, in the above-described embodiment, an example in which the protective film is applied to the cross portion between the source / drain electrode 110 and the gate electrode has been described. The same can be applied to the parts.

In all of the embodiments of the present invention described above, the common electrode 106 is described as being formed of a polycrystalline ITO film having a cubic bixbite type crystal structure. Is formed of Al, the method described in FIGS. 3 and 4 can be similarly applied. In this case, the common electrode 106 can be extracted without using the common extraction electrode 111. In this case, the common electrode and the source / drain electrode 110 form a cross portion, but the present invention can be applied to such a case.

Further, all of the embodiments of the present invention described above have been described as the liquid crystal display panels using the polycrystalline silicon TFTs.
The same applies to the case where a T, an insulating film diode or the like is used.

[0046]

As described above, according to the present invention,
Since the common electrode is formed of a polycrystalline ITO film having a cubic-byxbite type crystal structure having excellent etching resistance to hydrofluoric acid-based etchant,
The common electrode can be directly connected to the common extraction electrode without requiring an extra manufacturing step such as forming a common extraction lower electrode made of Al or the like, and without damaging the common electrode. By using the film as a protective film from a hydrofluoric acid-based etchant to protect the wiring and the cross portion of the wiring, the reliability of the wiring and the cross portion of the wiring can be improved.
Since the TO film also has excellent characteristics as a transparent conductive film, it also has an effect that a high-definition liquid crystal display panel having good characteristics can be obtained with high yield.

[Brief description of the drawings]

FIG. 1 is a diagram illustrating a cross-sectional structure and a manufacturing process thereof according to an embodiment of the present invention.

FIG. 2 is a diagram illustrating the etching resistance of a polycrystalline ITO film.

FIG. 3 is a cross-sectional view showing a configuration of another embodiment of the present invention using a polycrystalline ITO film as a protective film.

FIG. 4 is a cross-sectional view showing a configuration of still another embodiment of the present invention using a polycrystalline ITO film as a protective film.

FIG. 5 is a cross-sectional view showing a structure of an example of the related art.

[Explanation of symbols]

 101 Glass substrate 102,502 Polycrystalline silicon film 103,503 Gate oxide film 104,504 Gate electrode 105,505 Source / drain region 106,106 ', 507 Common electrode 107,508 Interlayer insulating film 108,109,509,510 Through Hole 110, 511 Source / drain electrode 111, 512 Common extraction electrode 112, 513 Pixel electrode 113, 514 Switching TFT section 114, 515 Charge holding capacitor section 115, 516 Common electrode extraction section 116-118 Protective film 501 Transparent substrate 506 Common Lower electrode for drawer

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification code FI H01L 27/12 H01L 29/40 A 29/40 21/88 M (72) Inventor Norihisa Ono 4026 Kuji-cho, Hitachi City, Ibaraki Prefecture Hitachi, Ltd.Hitachi Research Laboratories (72) Inventor Akio Mimura 4026, Kuji-cho, Hitachi City, Ibaraki Prefecture Hitachi, Ltd. In-house (56) References JP-A-60-97382 (JP, A) Annual report of the Faculty of Engineering, The University of Tokyo Vol. 46 (1987) pp. 189-192

Claims (9)

(57) [Claims] In a liquid crystal display panel, a plurality of electrodes made of metal are formed on a substrate of the liquid crystal display panel, an insulating film is formed on the plurality of electrodes, and A liquid crystal display panel on which a polycrystalline indium tin oxide film having a cubic-byxbite type crystal structure for protecting the plurality of electrodes against a hydrofluoric acid-based etchant is formed. 2. The plurality of electrodes correspond to a plurality of gate electrodes, a plurality of first source / drain electrodes intersecting the plurality of gate electrodes in a matrix, and a point of intersection of the plurality of first source / drain electrodes. A plurality of second source / drain electrodes connected to the formed active element; a plurality of common electrodes forming a capacitance between the plurality of second source / drain electrodes; 2. The liquid crystal display panel according to claim 1, wherein the liquid crystal display panel is at least one of the drawers. 3. The liquid crystal display panel according to claim 1, wherein an electrode formed below said polycrystalline indium tin oxide film is a gate electrode. 4. The liquid crystal display panel according to claim 1, wherein an electrode formed below said polycrystalline indium tin oxide film is a first source / drain electrode. 5. The liquid crystal display panel according to claim 1, wherein the electrode formed below the polycrystalline indium tin oxide film is a second source / drain electrode. 6. The method according to claim 1, wherein a transparent conductive film having a cubic bixbite type crystal structure is formed under the plurality of electrodes made of metal. Liquid crystal display panel. 7. A method of manufacturing a liquid crystal display panel in which a liquid crystal layer is sandwiched between a pair of substrates, a step of forming an electrode made of metal, and a polycrystalline oxide having a cubic bibite structure on the electrode. A step of forming an indium tin film, and a step of performing a hydrofluoric acid-based etchant after these steps. 8. The method according to claim 7, wherein the electrode formed in the step of forming an electrode made of a metal is a gate electrode. 9. The method for manufacturing a liquid crystal display panel according to claim 7, wherein the electrodes formed in the step of forming the electrodes made of metal are first or second source / drain electrodes. .