JPH04250426A - Active matrix array and its manufacture - Google Patents

Abstract

PURPOSE:To offer an active matrix array which has uniform and fine windows formed in a picture element electrode and also has an equipotential surface formed between the picture element electrode and a common electrode in parallel to a substrate as to the active matrix array whose picture element electrode is made of polycrystalline silicon. CONSTITUTION:The active matrix array consists of the picture element electrode 21 formed of polycrystalline silicon on the transparent insulating substrate 20, a switching element, a select signal electrode 11, and a data signal electrode 12. Many transparent and fine areas 22 are formed uniformly of silicon dioxide in the polycrystalline silicon picture element electrodes 21.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to active matrix arrays used in liquid crystal displays and the like.

0002

[Prior Art] Until now, transparent and conductive indium tin oxide (I
TO) has been used. When patterning ITO using a photolithography method, better patterning accuracy can be obtained by using a dry etching method than by using a wet etching method. but,
Up to now, a technique for patterning ITO by dry etching has not been established. Therefore, I
A wet etching method is used for etching TO, but this method results in poor patterning accuracy. Therefore, it has been proposed to use polycrystalline silicon heavily doped with impurities as a material to replace ITO (International Electro Device Meeting 1989, pp. 161-164). Unlike ITO, this polycrystalline silicon is not completely transparent in the visible light range, so in order to obtain a bright screen, the film thickness must be made thinner, and windows must be added by etching the pixel electrodes. Therefore, it is necessary to increase the transmittance by increasing the aperture ratio. As the shape of the window provided in this pixel electrode, a striped one has been proposed as shown in Figure 7 (1990, Proceedings of the Annual Conference of the Television Society of Japan,
P. 85-86). This stripe pattern is formed by patterning the pixel electrode 61 made of polycrystalline silicon by photolithography.

0003

On the other hand, when a window is provided in a pixel electrode, an equipotential surface is formed between the pixel electrode and the common electrode so that the alignment direction of liquid crystal molecules is perpendicular to the substrate. Must be parallel to the substrate.

[0004] When the pixel size is large, even if the stripe pattern of the window formed in the pixel electrode part is not fine,
The equipotential surface formed between the pixel electrode and the common electrode can be parallel to the substrate. However, when the pixel size is reduced and the size of the pixel electrode becomes smaller, the shape of the window provided on the pixel electrode must be changed in order to make the equipotential surface formed between the pixel electrode and the common electrode parallel to the substrate. Further miniaturization becomes necessary. At this time, if a fine pattern is etched on the pixel electrode by photolithography, there is a high possibility that residue will remain, resulting in non-uniform aperture ratio, and an equipotential surface formed between the pixel electrode and the common electrode. A problem arises in that the planes are no longer parallel to the substrate. The present invention provides an active matrix array in which uniform and fine windows are formed in the pixel electrodes even when the pixel size is small, and the equipotential plane formed between the pixel electrodes and the common electrode is parallel to the substrate. The purpose is to

[0005]

[Means for Solving the Problems] In the first invention, in an active matrix array in which polycrystalline silicon is used as a pixel electrode material and pixels are arranged in a matrix, the polycrystalline silicon pixel electrodes are locally replaced with silicon dioxide. It is characterized by forming a large number of transparent fine regions made of silicon dioxide on the polycrystalline silicon pixel electrode by changing its properties to .

A second invention is a method of manufacturing an active matrix array, characterized in that a polycrystalline silicon pixel electrode is formed by forming a silicon dioxide region by changing a polycrystalline silicon thin film into silicon dioxide. .

[0007]

[Operation] In the present invention, a part of the polycrystalline silicon pixel electrode is modified to silicon dioxide to form a transparent region that serves as a window, so the pixel electrode is not etched by photolithography as in the conventional method. Windows, which are transparent areas, can be formed to increase the aperture ratio. Further, when patterning fine windows on the polycrystalline silicon pixel electrode, no etching is performed, so that the aperture ratio does not become non-uniform due to residue or the like.

According to the method according to claim 3 of the second invention, oxygen ions can be selectively implanted into the polycrystalline silicon pixel electrode, and a silicon dioxide region can be formed only in the portion where oxygen ions are implanted. becomes possible. Furthermore, by using a mask having a fine pattern, a finely shaped window made of silicon dioxide can be formed on the polycrystalline silicon pixel electrode. Since polycrystalline silicon is not etched in this manner, the problem of non-uniform aperture ratio due to residue etc. that occurs during etching by photolithography is solved. Further, since the shape of the pixel electrode can be made fine, the equipotential surface formed between the pixel electrode and the common electrode can be made parallel to the substrate even when the pixel electrode size is small.

According to the method according to claim 4 related to the second invention, oxygen ions are implanted into the polycrystalline silicon thin film only in the portion where the polycrystalline silicon pixel electrode is irradiated with the oxygen ion beam, and a silicon dioxide region is formed. be done. Furthermore, by narrowing down the diameter of the oxygen ion beam, a finely shaped window made of silicon dioxide can be formed in the polycrystalline silicon pixel electrode. Since polycrystalline silicon is not etched in this manner, the problem of non-uniform aperture ratio due to residue etc. that occurs during etching by photolithography is solved. In addition, since it is possible to make the shape of the pixel electrode minute, the equipotential surface formed between the pixel electrode and the common electrode can be made parallel to the substrate even when the pixel electrode size is small. .

[0010] According to the method according to claim 5 related to the second invention, oxygen in the oxygen atmosphere is incorporated into the polycrystalline silicon thin film only in the portion of the polycrystalline silicon pixel electrode irradiated with the laser, and the silicon dioxide region is It is formed. Furthermore, by narrowing down the beam diameter of the laser, a finely shaped window made of silicon dioxide can be formed on the polycrystalline silicon pixel electrode. Since polycrystalline silicon is not etched in this manner, the problem of non-uniform aperture ratio due to residue etc. that occurs during etching by photolithography is solved. In addition, since it is possible to make the shape of the pixel electrode minute, the equipotential surface formed between the pixel electrode and the common electrode can be made parallel to the substrate even when the pixel electrode size is small. .

[0011]

[Embodiment] First, a first embodiment will be explained using FIGS. 1 and 2.

FIG. 1 is a plan view of an active matrix array in which polycrystalline silicon pixel electrodes are formed using the present invention, and FIG. 2 is a cross-sectional view taken along the line A-A' in FIG. In FIG. 1, 21 is a pixel electrode, 11 is a data wiring,
12 is a gate wiring.

As shown in FIG. 2, a transparent glass substrate 20
A pixel electrode 21 made of polycrystalline silicon is formed thereon, and a fine window 22 made of silicon dioxide is formed in this polycrystalline silicon pixel electrode. An insulating film 23 made of silicon dioxide is formed to cover the pixel electrodes 21 and 22. Furthermore, the pixel electrode 21
A contact hole 24 is formed in a part of the upper insulating film 23, and a high melting point, low resistance metal thin film such as molybdenum, titanium, tungsten, etc. and a silicified metal thereof are formed on the insulating film 23 through the contact hole 24. Source/drain electrodes 25 are formed of a laminated film of a compound thin film and a polycrystalline silicon thin film doped with impurities at a high concentration. Further, a semiconductor layer 26 made of polycrystalline silicon is formed between the source and drain electrodes 25 and partially covering the source and drain electrodes 25. A gate insulating film 27 made of silicon dioxide is formed on the semiconductor layer 26, the source and drain electrodes 25, and the insulating film 23. Further, a gate electrode 28 made of aluminum, chromium, etc. is formed on the gate insulating film 27 so as to cover a part of the semiconductor layer 26. A protective insulating film 28 made of silicon nitride is formed on the gate electrode 28 and the gate insulating film 27.

Next, an embodiment of the third aspect of the second invention will be described with reference to FIGS. 3 and 4. First, as shown in FIG. 3A, a polycrystalline silicon thin film heavily doped with phosphorus is formed to a thickness of 500 angstroms on a glass substrate 20 whose surface has been cleaned by CVD. Next, as shown in FIG. 3B, the polycrystalline silicon thin film is covered with a mask 30, and oxygen ions 31 are implanted at 30 keV using an ion implantation device, and then at 600° C. in a nitrogen atmosphere. Annealing is performed for 3 hours to form a window 22 made of silicon dioxide. Furthermore, as shown in FIG. 3C, the polycrystalline silicon thin film is etched by photolithography to form the pixel electrode 21. next,
As shown in FIG. 3(d), after forming a silicon dioxide thin film 23, which is an interlayer insulating film, to a thickness of 1000 angstroms, a part of the pixel electrode 21 is etched by photolithography to form a contact hole 24. do. Next, as shown in FIG. 3(e), thin films of high-melting-point, low-resistance metals such as molybdenum, titanium, and tungsten and their silicide compounds are formed to thicknesses of 1000 angstroms and 500 angstroms, respectively, by sputtering or vapor deposition. After forming a polycrystalline silicon thin film heavily doped with phosphorus to a thickness of 500 angstroms using the CVD method, the photolithography method was used to
The metal thin film, the silicide compound, and the polycrystalline silicon thin film are etched to form source and drain electrodes 25. Next, as shown in FIG. 4A, a polycrystalline silicon thin film is formed to a thickness of 500 angstroms by CVD, and then the polycrystalline silicon thin film is etched by photolithography to form a semiconductor layer 26. . next,
As shown in FIG. 4B, a silicon dioxide thin film that will become the gate insulating film 27 is formed to a thickness of 1500 angstroms by CVD. Next, as shown in FIG. 4C, a thin film of metal such as aluminum or chromium is formed to a thickness of 3000 angstroms by sputtering or vapor deposition, and then etched by photolithography to form the gate electrode 28. Form. Next, as shown in FIG. 4D, a silicon nitride thin film is formed as a protective insulating film 29 to a thickness of 3000 angstroms by plasma CVD.

Next, an embodiment of the fourth aspect of the second invention will be described. First, a polycrystalline silicon thin film doped with phosphorus at a high concentration is formed to a thickness of 500 angstroms on a glass substrate 20 whose surface has been cleaned, and then an ion implantation device having the configuration shown in FIG. The ion beam 47 is accelerated by an acceleration tube 42 at 30 keV, then deflected by an electric field generated by an X-axis scanner 46 and a Y-axis scanner 44, and irradiated onto the polycrystalline silicon thin film to form an ion beam made of silicon dioxide. The window 22 is scanned so that its distribution is uniform within the substrate surface. Next, as shown in FIG. 3C, the polycrystalline silicon thin film is etched by photolithography to form the pixel electrode 21. Thereafter, an active matrix array is manufactured using a process similar to that of the second invention.

Next, an embodiment of the fifth aspect of the second invention will be described. First, a polycrystalline silicon thin film doped with phosphorus at a high concentration was formed to a thickness of 500 angstroms on a glass substrate 20 whose surface had been cleaned.
Using a laser doping apparatus having the configuration shown in FIG.
An excimer laser beam 53 having an energy of 1 is irradiated, and the laser beam is scanned so that the formed window 22 made of silicon dioxide has a uniform distribution within the substrate surface. Next, as shown in FIG. 3(c), the polycrystalline silicon thin film is etched by photolithography to form the pixel electrode 21.
form. Thereafter, an active matrix array is manufactured using a process similar to that of the second invention.

By forming a silicon dioxide region in the polycrystalline silicon pixel electrode in this manner, the aperture ratio can be increased without performing etching by photolithography. Furthermore, by using the manufacturing method according to the second invention, a uniform and fine silicon dioxide region is formed within the substrate surface, so that the aperture ratio becomes uniform within the substrate surface, and furthermore, the common electrode and the pixel electrode are It becomes possible to make the equipotential surface formed in between parallel to the substrate.

The case where a staggered thin film transistor is used as a switching element has been explained above.
Similar effects can be obtained not only when using a planar structure thin film transistor but also when using a switching element other than a thin film transistor, such as an MIM (metal insulator metal) element.

[0019]

[Effects of the Invention] As explained above, according to the present invention, each pixel has a uniform aperture ratio within the substrate plane, and the equipotential surface formed between the pixel electrode and the common electrode is parallel to the substrate. We were able to obtain an active matrix array having polycrystalline silicon pixel electrodes.

[Brief explanation of the drawing]

FIG. 1 is a plan view of an active matrix array consisting of polycrystalline silicon pixel electrodes and thin film transistors according to the present invention.

FIG. 2 is a cross-sectional view taken parallel to a gate wiring near a thin film transistor of an active matrix array.

FIG. 3 is a manufacturing process diagram according to the manufacturing method according to claim 3 relating to the second invention of the active matrix array.

FIG. 4 is a manufacturing process diagram according to the manufacturing method according to claim 3 regarding the second invention of the active matrix array.

FIG. 5 is an explanatory diagram of the manufacturing method according to claim 4 relating to the second invention of the active matrix array.

FIG. 6 is an explanatory diagram of the manufacturing method according to claim 5 regarding the second invention of the active matrix array.

FIG. 7 is a plan view of an active matrix array with conventional polycrystalline silicon pixel electrodes.

[Explanation of symbols]

10 Data wiring 11 Gate wiring 20 Glass substrate 21 Pixel electrode 22 Window 23 Interlayer insulation film 24 Contact hole 25 Source, drain electrode 26 Semiconductor layer 27 Gate insulation film 28 Gate electrode 29 Protective insulation film 30 Mask 31 Oxygen ion 42 Acceleration tube 44 Y-axis scanner 46 X-axis scanner 47 Oxygen ion beam 53 Excimer laser light 61 Pixel electrode

Claims (5)

[Claims] 1. In an active matrix array comprising a pixel electrode made of polycrystalline silicon formed on a transparent insulating substrate, a switching element, a selection signal electrode, and a data signal electrode, the polycrystalline silicon pixel An active matrix array characterized in that the electrodes contain transparent fine regions made of silicon dioxide. 2. A method for manufacturing an active matrix array, comprising forming a polycrystalline silicon pixel electrode containing a large number of fine transparent regions by locally transforming a portion of a polycrystalline silicon thin film into silicon dioxide. . 3. In the step of forming a polycrystalline silicon pixel electrode according to claim 2, oxygen ions are introduced through a mask through the polycrystalline silicon thin film as a method of locally transforming a part of the polycrystalline silicon thin film into silicon dioxide. A method of manufacturing an active matrix array, characterized in that regions of silicon dioxide are formed by implantation. 4. In the step of forming a polycrystalline silicon pixel electrode according to claim 2, as a method of locally transforming a part of the polycrystalline silicon thin film into silicon dioxide, an oxygen ion beam is applied to the polycrystalline silicon thin film in an electric field. 1. A method of manufacturing an active matrix array, characterized in that a region of silicon dioxide is formed by irradiating the active matrix array with deflection. 5. In the step of forming a polycrystalline silicon pixel electrode according to claim 2, as a method of locally transforming a part of the polycrystalline silicon thin film into silicon dioxide, a laser beam is applied to the polycrystalline silicon thin film in an oxygen atmosphere. 1. A method for manufacturing an active matrix array, comprising forming a region of silicon dioxide by irradiating with.