JP4610992B2 - Manufacturing method of liquid crystal display device - Google Patents

Description

  The present invention relates to a method for manufacturing a liquid crystal display device, and more particularly to a method for manufacturing a liquid crystal display device including a step of patterning a transparent film.

  A widely used twisted nematic (TN) liquid crystal display device has a large viewing angle dependency. In recent years, liquid crystal display devices are required to improve display performance such as high definition, high brightness, and high quality. A multi-domain type is known as a liquid crystal display device capable of expanding a viewing angle. In the multi-domain vertical alignment (MVA) method, the rubbing is not used but the extending protrusions are used, so that the pre-tilt in the opposite direction is given to the vertically aligned liquid crystal molecules on both sides of the protrusions, thereby realizing the multi-domain. In addition to providing protrusions that extend to the color filter substrate, a transparent pixel electrode having slits is formed on the thin film transistor substrate, and in addition to pretilt on both sides of the protrusions, a fringe electric field is generated at the slits when voltage is applied for multi-domain display. A method to do this has also been proposed.

JP 2004-221935 A JP 2003-315814 A Japanese Patent Laid-Open No. 10-253594 JP 2003-140138 A FUJITSU, 49,3, pp175-179 (05, 1998)

  The transparent electrode pattern of the liquid crystal display device may be disturbed. If the width of the narrow slit pattern to be exposed with a uniform dimension becomes non-uniform, uneven brightness or the like will occur in the display. An exposure technique that does not cause pattern disturbance is desired.

According to one aspect of the present invention, a step of forming a thin film transistor on the surface of the transparent insulating substrate, a step of forming a light shielding film on the back surface of the transparent insulating substrate, and a transparent film above the surface of the transparent insulating substrate on which the thin film transistor is formed. Forming a resist pattern by applying a resist layer on the transparent film and exposing from above the resist layer ; and processing the transparent film using the resist pattern as a mask; And a step of removing the light-shielding film.

  The stage of the exposure apparatus is black so as not to generate reflected light. However, with use, the surface of the structure on the stage becomes worn, and the metal surface that is the base of the black surface is exposed. Then, exposure light was reflected on the exposed metal surface, and secondary exposure was performed from the back surface, and it was found that the pattern accuracy was disturbed. By providing a light-shielding film on the back surface of the transparent substrate, the structure on the stage is not exposed to light, and pattern accuracy can be prevented from being disturbed.

Hereinafter, an MVA liquid crystal display device will be described as an example without any limitation.
FIG. 1 is a cross-sectional view of an MVA liquid crystal display device. A thin film transistor (TFT) substrate 10 and a color filter substrate 20 are disposed to face each other, and a vertically aligned liquid crystal layer 30 is sandwiched therebetween.

  The TFT substrate 10 has a transparent pixel electrode 12 such as indium-tin-oxide (ITO) above the surface of a transparent insulating substrate 11 such as glass. The transparent pixel electrode 12 includes a slit 13. A vertical alignment film 14 is formed on the outermost surface, but is not rubbed. As will be described later, a TFT, its wiring, a storage capacitor, and the like are also formed on the TFT substrate.

  The color filter substrate 20 has a light-shielding black stripe 22 that defines a pixel display area on a transparent insulating substrate 21 such as glass. The black stripe can be formed of a metal such as Cr or Mo or a black resin containing a black pigment. A color filter layer 23 such as three primary colors is formed in the display region so as to cover the black stripe. A transparent common electrode 24 such as ITO is formed so as to cover the color filter layer 23. If necessary, a planarizing layer may be provided under the transparent common electrode with the same kind of resin as the resist. Protrusions 25 that selectively extend on the transparent common electrode are formed of resin or the like, and a vertical alignment film 26 is formed on the outermost surface. The vertical alignment film is not rubbed.

  The liquid crystal layer 30 includes vertically aligned liquid crystal molecules 31. On the protrusion 25, the liquid crystal molecules are aligned perpendicular to the surface, so that the liquid crystal molecules have a pretilt in the opposite direction on both sides of the protrusion. When a voltage is applied between the transparent electrodes 12 and 24, the direction in which the liquid crystal molecules are tilted is determined according to the pretilt. If the dielectric constants of the projection and the liquid crystal layer are different, the projection also exhibits the action of bending the lines of electric force.

  Between the flat electrodes, basically, the electric force lines 33 perpendicular to both the substrates are generated. However, since there is no pixel electrode in the slit 13, the electric force lines generated from the common electrode facing each other are bent to form a transparent pixel electrode. To reach. That is, a fringe electric field is generated. Since the liquid crystal layer 30 has a thickness of several microns, a slit width for bending the lines of electric force of several microns is sufficient. It is desirable to arrange the protrusions 25 and the slits 13 regularly and uniformly. For example, when the slit width changes, the fringe electric field changes and the alignment of liquid crystal molecules is disturbed.

  2A and 2B are a cross-sectional view and a plan view further illustrating the configuration and manufacturing process of the TFT substrate. A broken line in the plan view of FIG. 2B corresponds to the cross section of FIG. 2A. A metal layer such as Mo or Al is formed on a transparent substrate 10 such as glass and patterned to form a gate electrode and a gate wiring G. A gate insulating film GI such as silicon oxide is formed so as to cover the gate wiring, and a polycrystalline or amorphous silicon layer is formed thereon, and is patterned using photolithography to form a channel layer CH.

  After patterning the channel layer CH, an etch stopper layer such as a silicon nitride layer is formed, a resist layer is applied thereon, and exposed from the back surface to form a resist pattern. Using this resist pattern as a mask, the etch stopper layer is patterned to form a channel protective film CPR. The channel layer CH is exposed at both ends of the channel protective film CPR.

  A low resistance polycrystalline or amorphous silicon layer 15 doped with n-type impurities, a metal layer such as Ti, Al, etc. are stacked, and a source region S and a drain region D connected to both sides of the channel region CH by photolithography and etching. To leave a pattern. As shown in FIG. 2B, a drain wiring DL is also formed continuously with the drain region. Although the conductive layer on the channel region CH is removed by etching, the channel layer CH is not damaged because the channel protective layer CPR functions as an etch stopper.

  An insulating layer 12 such as silicon oxide is formed on the substrate so as to cover the source region S and the drain region D, and the contact opening OP is opened by etching. A transparent conductive layer 12 such as ITO is formed on the insulating film 12, and a photoresist layer PR is applied on the surface thereof.

  As shown in FIG. 2B, for example, the storage capacitor line SCL is formed simultaneously with the gate wiring G, and the storage capacitor electrode SC is formed simultaneously with the creation of the source S and drain D. A contact opening OP penetrating the insulating layer 12 is also formed on the storage capacitor electrode SC. The method for creating the storage capacity is not limited to the above. Various known configurations can be employed.

Conventionally, the photoresist layer PR was exposed in the configuration as described above. A region where the metal layer and the low-resistance silicon layer are not present becomes a light-transmitting region through which light is transmitted.
In this embodiment, a light shielding film 19 is provided on the back surface of the transparent substrate 10. When the channel protective film CPR is formed by using the back exposure, the light shielding film 19 is formed after the channel protective film CPR is formed and before the resist layer PR is exposed. The material of the light shielding film 19 is not particularly limited as long as it has a light shielding property. It can be formed of resin or the like.

  When Mo or Al is used as the metal layer of the TFT substrate, the Mo layer or Al layer can be formed using the same film forming apparatus. Further, the Mo layer and the Al layer can be simultaneously removed when the resist pattern is removed by wet processing.

  FIG. 3 shows an exposure process for patterning the ITO layer 12. On the exposure stage 41, a TFT substrate having a light shielding film 19 formed on the back surface is disposed. On the exposure stage 41, a structure 42 such as a groove for attracting the substrate and a pin for lifting the substrate is disposed.

  The structure of such an exposure stage has a tendency that the surface is worn by use, the black paint is peeled off, and the underlying metal surface such as aluminum is exposed. When exposure is performed using a TFT substrate having no light shielding film 19 shown in FIG. 2A, exposure light passes through the TFT substrate in the light-transmitting region. If a highly reflective surface such as aluminum is present, the exposure light is reflected, and the photoresist layer PR is secondarily exposed from the back surface. It was found that this was the cause of pattern accuracy disturbance.

  An exposure mask 44 having a light shielding metal pattern 43 is disposed above the TFT substrate, and ultraviolet light 45 is irradiated from above to expose the photoresist layer PR in proximity. In a region where the light shielding metal pattern 43 does not exist, the ultraviolet light 45 enters the photoresist layer PR and performs selective exposure. When the photoresist layer PR is a positive resist, when it is developed, the resist layer is removed in the exposed region, and only the unexposed portion remains. The ITO layer 12 is etched and patterned using the photoresist pattern thus formed as a mask. Since the light shielding layer 19 on the back surface of the TFT substrate prohibits the passage of light, the light is prevented from entering the structure 42 of the stage 41. In this way, by preventing non-uniform reflection on the exposure stage, it is possible to form a highly accurate photoresist pattern according to the mask.

  After patterning the ITO layer, when the resist pattern is removed with an alkaline solution, the Mo layer on the back surface is removed at the same time. Similarly, when Al is used for the light shielding layer, it can be removed with an alkaline developer.

  As described above, the reflected light is generated from the structure of the exposure stage, so that the photoresist layer can be prevented from being secondarily exposed from the back surface, and a highly accurate resist pattern originally required can be configured. Partial display unevenness that has occurred in the slit portion of ITO can be suppressed.

  Although the present invention has been described with reference to the embodiments, the present invention is not limited thereto. The present invention can be applied to a manufacturing method of a liquid crystal display device including patterning of a transparent film during the manufacturing process. For example, the liquid crystal display device is not limited to the MVA method. The method described above can be used not only for patterning the transparent electrode but also for patterning the transparent film. It can be used for contact opening formation of a transparent insulating layer, patterning of a channel protective layer, and the like. The photoresist may be positive or negative. It will be apparent to those skilled in the art that other various modifications, improvements, and combinations are possible.

It is sectional drawing which shows the structure of a liquid crystal display device roughly. It is sectional drawing and a top view which show the structure of a TFT substrate roughly. It is sectional drawing which shows the exposure process of an ITO layer roughly.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 TFT substrate 11 Glass substrate 12 Transparent electrode 13 Slit 14 Alignment film 20 Color filter substrate 21 Transparent substrate 22 Black stripe 23 Color filter 24 Transparent electrode 25 Extension protrusion 26 Light distribution film 30 Liquid crystal layer 31 Liquid crystal molecule PR Photoresist layer S Source D drain CH channel CPR channel protective layer DL drain line SCL storage capacitor line SC storage capacitor OP contact opening 41 exposure stage 42 exposure stage structure 43 light shielding pattern 44 mask 45 ultraviolet light

Claims (5)

Forming a thin film transistor on the surface of the transparent insulating substrate;
Forming a light shielding film on the back surface of the transparent insulating substrate;
Forming a transparent film above the surface of the transparent insulating substrate on which the thin film transistor is formed;
Applying a resist layer on the transparent film, exposing from above the resist layer to form a resist pattern; and
Processing the transparent film using the resist pattern as a mask;
Removing the light shielding film;
A method for manufacturing a liquid crystal display device comprising:   The method for manufacturing a liquid crystal display device according to claim 1, wherein the light shielding film is formed of Al, Mo, Ta, Cr, Ti, or an alloy thereof, silicon, or black resin.   The method of manufacturing a liquid crystal display device according to claim 1, wherein the light shielding film is formed of Mo or Al, and the step of removing the light shielding film also removes the resist pattern.   The method for manufacturing a liquid crystal display device according to claim 1, wherein the transparent film is a transparent conductive film.   The liquid crystal display device includes a counter substrate having a color filter and an extended protrusion, and the step of performing the processing uses the resist pattern having a slit having a shape corresponding to the extended protrusion as a mask. The method of manufacturing a liquid crystal display device according to claim 4, wherein the conductive film is etched to form a transparent pixel electrode.

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