JP2000243743A - Organic molecular film removal device using ultraviolet rays and removal thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a simple method for completely removing an organic molecular film on a substrate. SOLUTION: An organic high-molecular film to be removed on a substrate is exposed to ultraviolet rays of a wavelength of 180 nm or shorter, whereby the film is completely decomposed and can be removed. Moreover, since the ultraviolet rays of the wavelength of 180 nm or shorter are hardly transmitted to a transparent conductive oxide, such as an ITO(indium-tin oxide), the rays can be used for removing a polyimide orientation film having defects, such as a defective printing, on a TFT array board with an ITO transparent electrode pattern formed on the surface of the structure of a TFT. By having the polyimide orientation film on the TFT array board irradiated with the rays of wavelength of 180 nm or shorter, the defect orientation film on the TFT array board can be completely removed, without giving adverse effects to the characteristics of the TFT. After that, the defective orientation film is again sent to an orientation film forming process. Similarly, by having the TFT array board irradiated with the rays of the wavelength of 180 nm or shorter prior to an adhesion of an orientation film to the TFT array board, impurities in the TFT array board can be also removed.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for removing an organic molecular film, and more particularly to a simple method for completely removing a polyimide film as an alignment film in manufacturing a color filter substrate of a liquid crystal display device. Complete removal of the polyimide film is essential for reworking the color filter substrate. The present invention also relates to a method for removing an organic molecular film on an array substrate.

[0002]

2. Description of the Related Art In a manufacturing process of a liquid crystal display device cell, after a color filter structure or an array structure is formed on a substrate,
There is a step of forming an organic polymer film for aligning liquid crystal molecules. Here, a polyimide resin (P
A film such as I) or polyvinyl alcohol (PVA) is used, and is adhered to the entire surface of the substrate by printing or spin coating. Then, it is baked and subjected to an alignment treatment such as rubbing to form an alignment film. However, when the organic polymer alignment film formed here has a defect, the entire substrate has been discarded as a defective substrate. Discarding and discarding a substrate including a color filter structure and an array structure manufactured by using a very advanced manufacturing technique for high density and high definition of a display device increases manufacturing cost.

[0003] Therefore, attempts have been made to peel off the defective organic polymer alignment film once, form a new film, and regenerate the film. At present, a technique for removing a photoresist in a semiconductor manufacturing process or the like is applied to the peeling of the organic polymer film. For example, as a wet etching method, there is a method of dissolving and removing with a solvent. In the case of a polyimide film, γ-butyrolactone and N-methylpyrrolidone (N
MP) and the like, but polyimide cannot be completely removed even by using such a solvent, and 10 to 10
About 100 ° of polyimide remains. As a dry etching method, there are a plasma etching method and an ozone ashing method. With these methods, complete removal of polyimide can be expected, but for that, a vacuum device and a dedicated ozone generator are required, and relatively expensive and complicated devices and processes are required as compared with other methods, It has not been put to practical use. Further, it is necessary to rotate or swing the substrate, and substrates of various sizes, in particular, 60
There is also a disadvantage that it is difficult to cope with a large substrate such as 0 × 720 mm.

Japanese Patent Application Laid-Open No. 6-202111 discloses a method of removing a polyimide liquid crystal alignment film having a wavelength of 230 to 300 nm.
It describes that after irradiating m ultraviolet rays, it is immersed in a polar solvent or an alkaline solvent. However, wavelength 2
Ultraviolet light of 30 to 300 nm is irradiated with ITO (Indium-T
In-Oxide) It was found that only a few percent of the transparent conductive film was transmitted, causing damage such as fading to the dye of the color filter thereunder. In addition, the wavelength 230 to 30
It was found that the polyimide film could not be completely removed only by the irradiation of 0 nm ultraviolet rays.

As described above, conventionally, the organic polymer film on the liquid crystal display cell substrate is completely reworked in order to rework defects such as defective printing or damage during alignment treatment such as rubbing. There was no suitable method for removal.
In order to improve the production yield of the liquid crystal display device and reduce the production cost, there is a need for an inexpensive and simple method for completely removing the organic polymer film such as polyimide adhered to the substrate.

[0006]

SUMMARY OF THE INVENTION An object of the present invention is to provide a simple method for completely removing an organic polymer film on a substrate.

Another object of the present invention is to provide a simple method for completely removing a polyimide film as an alignment film in manufacturing a liquid crystal display device. Complete removal of the polyimide film is essential for substrate rework. Accordingly, another object of the present invention is to provide a method for improving the manufacturing yield of a liquid crystal display device cell.

Another object of the present invention is to provide a simple apparatus for completely removing an organic polymer film on a substrate.

[0009]

According to the present invention, an organic polymer film to be removed on a substrate can be decomposed and removed by exposing it to ultraviolet light having a wavelength of 180 nm or less.
Such a removing method is useful, for example, when removing an alignment film made of an organic polymer such as polyimide in the production of a liquid crystal display device for reproduction.

As shown in FIG. 1, the mechanism is considered to be the breaking action of each bond of the organic molecule by the energy of the irradiated ultraviolet light, and the oxidizing action by oxygen in the atmosphere excited by the ultraviolet energy. .
Generally, the bond energy (eV / molecule) between main atoms contained in an organic molecule is represented by a C—N bond (3.02), a C—C
Bond (3.60), CH bond (4.29), C 、 C bond (6.29) and the like. Conventional output wavelength 254nm
E = hc / eλ where h is the Planck constant (6.626 × 10
^-34 [Jsec]), c is the speed of light (2.998 × 10
⁸ [m / sec]), and e is the energy of one electron (1.
602 × 10 ^-19 [J / eV]), and λ is the wavelength of light [m].
It is. ) Is 4.88 eV, which is lower than the binding energy of the C ＝ C bond. In other words, it can be seen that the C = C bond is not broken by irradiation with ultraviolet light having a wavelength of 254 nm.
So, for example, a polyimide structure

Embedded image In the above, the pyromellitic acid portion and the condensed ring portion remain without being decomposed. On the other hand, ultraviolet light having a wavelength of 180 nm can provide energy of 6.89 eV, which is sufficient to break the C = C bond. Therefore, it is possible to break and decompose interatomic bonds contained in most organic molecules.

The oxygen in the atmosphere irradiated with ultraviolet rays is

Embedded image As shown in the above, an excited oxygen atom O ^* is generated. This excited oxygen atom O ^* easily reacts with each atom or atomic group cut by ultraviolet rays, for example, by converting C, N, and H atoms into CO ₂ , NO _x , and H ₂ O molecules, respectively. And Since these move from the substrate to the atmosphere as gas molecules, they are easily removed by evacuation. Alternatively, it is conceivable that an excited oxygen atom directly attacks an organic molecule and oxidizes it to generate a similar oxide gas molecule.

However, ultraviolet rays having a wavelength shorter than 180 nm may cause damage such as decomposition of necessary materials contained in the structure below the organic polymer film to be removed due to its high energy. . For example, in a color filter substrate of a liquid crystal display device, if the dye portion is directly exposed to ultraviolet rays, the dye portion suffers damage such as fading.
However, usually, a color filter substrate has a transparent electrode pattern of ITO or IZO (Indium-Zinc-Oxide) formed on the surface of a dye portion, and these materials have a thickness of 180 nm.
It was found that almost no ultraviolet light having a wavelength of less than m was transmitted, and the film formed a protective film for the dye portion. Therefore, according to the method of the present invention, the removal of the polyimide alignment film on the substrate including the color filter structure, which was conventionally difficult, can be easily performed.

On the other hand, in a typical array substrate of a liquid crystal display device (FIG. 4A), when the semiconductor layer is directly exposed to ultraviolet rays, the transistor characteristics are adversely affected, and the gate insulating film has an electric charge. Inconveniences such as charging are caused. For example, in the TFT characteristics, the gate threshold voltage Vth shifts low and the drain off current Io
A characteristic change in which ff rises occurs. As a result, the leakage of the retained charges increases, which causes display quality defects such as bright spots (always white display of pixels) in the liquid crystal display device. However, in the array substrate structure with an organic film shown in FIG.
It was found that the lower semiconductor layer was protected by the structure covered with O or IZO. This array structure with an organic film
In order to improve the aperture ratio of an active matrix substrate having a TFT element, a transparent electrode is provided on the TFT structure via an organic insulating film. Therefore, removal of the polyimide alignment film on the substrate including the array substrate structure with the organic film can be easily performed.

The thickness of the transparent conductive film of ITO or IZO formed on these substrates is usually about 1500 ° in order to maintain a high transmittance in the visible light region.
It is enough to shield ultraviolet rays of 180 nm or less.

Further, in view of the above mechanism, it can be easily understood that the object to be decomposed and removed is not limited to the organic polymer film but extends to various organic molecules. Such organic molecules also include impurities that adhere to the substrate during the manufacturing process. Therefore, the removal apparatus and method of the present invention are usefully applied to, for example, removal of resist residues, removal of cleaning residues, cleaning of surface impurities, and the like in a manufacturing process of microelectronic products such as semiconductor devices as well as liquid crystal display devices. it can.

[0016]

DESCRIPTION OF THE PREFERRED EMBODIMENTS In the present invention, an organic polymer film to be removed on a substrate is decomposed and removed by exposing it to ultraviolet light having a wavelength of 180 nm or less.

FIG. 2 schematically shows a removing apparatus suitable for carrying out the present invention. The removal apparatus 100 includes an ultraviolet irradiation apparatus 110, an irradiation stage 120 on which the substrate 50 is placed and set at an irradiation position, and an ozone O ₃ generated by the irradiation of the ultraviolet light. The structure includes an ozone filter 130 and an ozone sensor 140. The chamber 101 further includes a carry-in conveyor 150 for carrying a substrate having organic molecules such as an organic polymer film to be removed and a carry-out conveyor 160 for carrying out a substrate from which organic molecules such as an organic polymer film have been removed. Is desirable. Further, if necessary, it is desirable to provide a means 170 for monitoring that organic molecules such as an organic polymer film to be removed are completely removed.

The ultraviolet irradiation device 110 useful for the present invention is:
It mainly outputs a wavelength of 180 nm or less.
The output depends on the type and thickness of organic molecules such as an organic polymer film to be removed, but at least about 4 mW / c
m ² , preferably about 8 mW / cm ² or more. As such an ultraviolet irradiation device, for example, USHIO Inc. (2-6 Otemachi, Chiyoda-ku, Tokyo)
1) Heya Shot Co., Ltd. (Shinjuku, Shinjuku-ku, Tokyo 3-
There is an excimer lamp (trade name) available from 23-7). This excimer lamp is 172 nm
At a wavelength of 4 to 30 mW / cm ² . In addition, D2 lamp (deuterium lamp)
And argon lamps and krypton lamps.

As shown in the chemical formula 2, oxygen in the chamber atmosphere generates ozone together with excited oxygen atoms when irradiated with ultraviolet rays. The ultraviolet light having a wavelength of 180 nm or less used in the present invention has high energy, and it can be seen that when irradiated in a normal environment, ozone or excited oxygen atoms having a concentration exceeding 1000 ppm are generated directly under the ultraviolet irradiation device. ing. This concentration is sufficient to remove normal organic molecules, and therefore does not require an additional ozone generator. As is well known, ozone has a strong poisoning effect and is harmful to the human body, so it must be decomposed in the chamber and exhausted to the outside of the chamber only after being converted into a safe substance. Therefore, an ozone sensor 140 for monitoring the ozone concentration in the chamber and an ozone filter 130 for safely removing ozone are required. These can utilize the well-known and usual apparatus. The chamber 101 must be sufficiently sealed so that ozone does not leak out of the chamber 101. However, on the other hand, during the removal of the organic molecules such as the organic polymer film to be removed, oxygen is consumed in the chamber atmosphere, and decomposition products such as CO ₂ , NO _x , and H ₂ O increase. In order to maintain the inside of the inside at a constant atmosphere, it is desirable to provide appropriate intake and exhaust means (not shown).

An irradiation stage 120 for transporting and supporting a substrate, and a carry-in conveyor 150 and a carry-out conveyor 1
60 is well known to those skilled in the art. Irradiation stage 1
Reference numeral 20 denotes an X-Y as movable in the horizontal and vertical directions for setting the irradiation position and can be fixed at an appropriate position.
There is a stage and a Z stage.

Optionally, means for heating the substrate may be provided. For example, a substrate temperature of 100 to 120 ° C.
By doing so, the speed at which the organic molecules are removed is increased about three times. As a means for heating the substrate, a heater may be incorporated in the irradiation stage so that the temperature of the irradiation stage surface can be adjusted, or a chamber equipped with a temperature control device may be used to adjust the temperature of the entire chamber. Good.

The means 170 for monitoring the complete removal of organic molecules such as the organic polymer film to be removed includes:
The substrate surface is irradiated with electromagnetic radiation such as infrared rays, and information on the substrate surface is obtained by the spectrum of reflected or scattered waves, or CO ₂ and NO _x generated by decomposition when organic molecules are irradiated with ultraviolet rays. It is conceivable to measure the concentration of such a substance in the chamber. Irradiating the substrate with unnecessarily more ultraviolet light may cause undesired damage to the substrate. Therefore, it is desirable to terminate the irradiation when organic molecules such as an organic polymer film to be removed are completely removed. Therefore, when the monitoring means 170 detects the end of the removal,
A configuration that sends a signal to the irradiation device 110 to end irradiation may be provided.

As an alternative, an illuminometer for monitoring the output from the ultraviolet irradiation device can be provided. in this case,
The irradiation time is determined based on the irradiation amount of the ultraviolet rays.

The invention of the present application is particularly useful for reproduction involving removal of a polyimide alignment film on each substrate forming a liquid crystal display, which has been difficult in the past. Here, the manufacture of this color filter substrate will be described as an example.
It will be easily understood that the present invention is applicable to removal of the organic polymer film on another substrate.

A typical color filter substrate for a liquid crystal display has a structure as shown in FIG. The color filter substrate has a structure including a black matrix pattern and a dye portion formed on a transparent substrate. A layer of a transparent conductive oxide such as ITO or IZO is formed as a transparent electrode on the dye portion. The transparent conductive oxide layer is
It depends on parameters such as conductivity and transmittance required for the color filter substrate.
Å, usually about 1300 to about 1700Å.

An alignment film is formed on the color filter substrate. As the alignment film, an organic polymer film such as a polyimide resin is used, and is attached to the entire surface of the substrate by printing or spin coating. The organic polymer membrane has a thickness of up to about 1000 °, usually about 600 to about 800 °. After attachment, the organic polymer film is baked and subjected to an alignment treatment such as rubbing or energy beam irradiation to complete an alignment film. The obtained alignment film is inspected by a visual inspection or an automatic optical inspection machine, and when a defect such as printing failure, foreign matter adhesion, scratch or peeling is detected, the color filter substrate together with the color filter substrate is subjected to a regeneration process as a defective substrate. The regeneration step includes a step of removing the defective alignment film from the color filter substrate and a step of forming the alignment film again.

The defect alignment film is removed from the color filter substrate using the organic polymer film removing device 100 of the present invention. First, the defective substrate 50 is carried into the chamber 101.
The carry-in conveyor 150 may be used for carrying in. The loaded substrate 50 is fixed to the irradiation stage 120 in the chamber, and then the horizontal position is determined so as to enter an appropriate irradiation range. Further, the vertical position is determined so as to be placed at a proper irradiation distance (about 5 mm or less, preferably about 1 to about 2 mm). After fine adjustment of the horizontal and vertical positions is performed so that the substrate 50 is set at an appropriate irradiation position, the position of the substrate 50 is fixed.

Next, a wavelength of 18
Ultraviolet rays of 0 nm or less are emitted, and the polyimide alignment film, which is the organic polymer film 60 to be removed, on the defective substrate 50 is exposed to the ultraviolet rays. Irradiation to the substrate 50 may be performed only for an empirically determined time, and is terminated when the monitoring means 170 confirms that the film 60 has been completely removed from the substrate 50. You may. The irradiation time varies depending on parameters such as the type and thickness of the organic polymer film to be removed and the wavelength and output of the irradiated ultraviolet light, but is usually on the order of several minutes to several tens of minutes. For example, in the case of a polyimide resin alignment film of about 700 °, ultraviolet rays having a wavelength of 172 nm (illuminance of light source: 8 mW / cm ² ) are irradiated for about 10 to about 30 minutes. Ozone generated during the irradiation of ultraviolet rays is monitored by an ozone sensor and processed by an ozone filter. Decomposition products from the organic polymer film are discharged by an appropriate method.

After the defect alignment film, which is the organic polymer film to be removed, is removed from the substrate and the irradiation of the ultraviolet rays is stopped, the substrate 50 fixed to the irradiation stage is released, and the substrate 50 is unloaded. It is carried out of the chamber 101 by the conveyor 160. The polyimide alignment film is completely removed from the color filter substrate after the irradiation with the ultraviolet light, and there is no need for further cleaning. In addition, since the dye portion is protected by the ITO transparent conductive film or the IZO transparent electrode,
There is no damage such as fading, and the color filter substrate can be reproduced without deterioration.

The color filter substrate from which the defective alignment film has been completely removed can be regenerated by performing an alignment film forming step again.

[0031]

[Example 1] As a transparent electrode, an about 1500 mm thick IT
A color filter substrate having an O film was prepared, and a polyimide resin having a thickness of about 700 ° was adhered thereon to prepare a sample substrate. When the sample substrate is
72 nm ultraviolet light (light source illuminance: 7.8 mW / cm ² )
For 30 minutes.

The surface of the sample substrate before and after the ultraviolet irradiation is
The result measured by X-ray photoelectron spectroscopy (XPS) is shown in FIG. As shown in FIG. 5A, the presence of each of C, N, and O atoms was confirmed on the sample substrate surface before irradiation, and thus it was found that the polyimide resin covered the substrate surface. On the other hand, as shown in FIG. 5B, N is not present on the surface of the sample substrate after irradiation, and O is present on the surface of the sample substrate.
And the presence of In and Sn was newly confirmed. this is,
This is considered to mean that the polyimide resin was substantially completely removed by the ultraviolet irradiation, and the underlying ITO film appeared on the surface. The signal attributable to C shown in FIG. 5 (b) is at a normal base level and does not indicate the remaining polyimide resin. The surface of the sample substrate after irradiation was observed by AFM (Atomic Force Microscopy), but no polyimide resin was found.

The optical characteristics as a color filter of the sample substrate before and after the ultraviolet irradiation were examined. No change was observed in both transmittance and chromaticity before and after irradiation.

[0034]

Comparative Example 1 The same sample substrate as in Example 1 was exposed to ultraviolet light having a wavelength of 254 nm for 30 minutes. However, it was confirmed by visual inspection that the polyimide resin remained on the sample substrate after being irradiated with ultraviolet light having a wavelength of 254 nm, and further, discoloration of the dye portion was observed.

[0035]

Example 2 On the sample substrate after irradiation with ultraviolet light obtained in Example 1, a new polyimide resin was printed in the same manner as in Example 1 to obtain a rework substrate. The newly-adhered polyimide resin film did not cause printing defects such as being repelled on the surface of the sample substrate after the ultraviolet irradiation.

[0036]

Example 3 A liquid crystal display device was assembled using the rework substrate obtained in Example 2. Further, the liquid crystal display device was placed under the conditions of 70 ° C. and 80% RH, and a high-temperature and high-humidity operation test (THB) was performed for 300 hours. The display characteristics before and after the test (display quality, luminance, gradation, contrast, visual field, etc.) were equivalent to those of a liquid crystal display device using a good sample substrate which was not a rework substrate.

[0037]

Embodiment 4 A sample substrate similar to that of Embodiment 1 was heated at a wavelength of 172 while heating the substrate surface to about 110 ° C.
ultraviolet light (light source illuminance: 7.8 mW / cm ² )
It was exposed for 0 minutes. Observation of the surface of the sample substrate after ultraviolet irradiation revealed that no polyimide resin was present.

Embodiment 5 As a transparent electrode, an about 1500 mm thick IT
An array substrate with an organic film having an O film was prepared as a sample substrate. This sample substrate was set at a wavelength of 172 nm.
(Illuminance of light source: 7.8 mW / cm ² ) for 1 minute.

T on the sample substrate before and after UV irradiation
FT characteristics were investigated by measuring the relationship between gate voltage and drain current. The result is shown in FIG. No change in characteristics was observed before and after irradiation.

[0039]

Comparative Example 2 An array substrate having the same structure as that of Example 5 except that it did not have an organic film and an ITO film was manufactured in the same manner as in Example 5 except that the wavelength was 1
It was exposed to ultraviolet light of 72 nm for 1 minute. The characteristics of the TFT on the array substrate without the ITO film before and after the ultraviolet irradiation were examined by measuring the relationship between the gate voltage and the drain current. As shown in FIG. 6B, after the irradiation, a change was observed in which the gate threshold voltage shifted to a lower level and the drain off current increased significantly as compared to before the irradiation.

[0040]

[Embodiment 6] An IT having a thickness of about 1500 mm was used as a transparent electrode.
An array substrate with an organic film having an O film on which a polyimide resin having a thickness of about 700 ° was adhered was prepared as a sample substrate. This sample substrate was set to a wavelength of 172n.
m UV (light source illuminance: 7.8 mW / cm ² )
Exposure for a minute. Observation of the surface of the sample substrate before and after ultraviolet irradiation revealed that no polyimide resin was present. The TFT characteristics before and after the irradiation of the ultraviolet rays were measured in the same manner as in Example 5, but no change in the characteristics was observed.

[Brief description of the drawings]

FIG. 1 is a conceptual diagram showing the principle of the present invention.

FIG. 2 is a schematic view showing a removing apparatus suitable for carrying out the present invention.

FIG. 3 is a schematic sectional view showing a structure of a color filter substrate.

FIG. 4 is a schematic sectional view showing the structure of an array substrate.
(A) shows the structure of a TFT array substrate without an organic film and a transparent electrode typically used so far, and (b)
Shows an array substrate structure with an organic film.

FIG. 5 is a spectrum showing the results of surface XPS analysis of a color filter substrate which has been subjected to a removal treatment according to the present invention before (a) and after (b) ultraviolet irradiation.

FIG. 6 shows a change in TFT characteristics of an array substrate structure with an ITO film and an organic film (a) and an array substrate structure without an ITO film and an organic film (b) before and after irradiation with ultraviolet light of 172 nm, respectively. It is a voltage-drain current curve.

Claims (1)

[Claims] An organic substance on a TFT array substrate is removed, comprising: preparing a TFT array substrate having a transparent conductive film formed on a surface thereof; and exposing the substrate to ultraviolet light having a wavelength of 180 nm or less. Method.