JP2007193371A - Liquid crystal display device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a liquid crystal display device capable of materializing high yield by using a simple manufacturing process. <P>SOLUTION: The liquid crystal display device is provided with pixel electrodes which constitutes, in one pixel, a reflection electrode constituting a reflection part for reflecting external light and a transmission electrode constituting a transmission part for transmitting light from a back surface light source, on one substrate of a pair of substrates arranged opposite to each other via a liquid crystal layer. Further, the liquid crystal display device includes: a first metal thin film which is formed on the one substrate and is made of the same layer with a gate electrode; a second metal thin film which is formed via the first metal thin film and a first insulating film and is made of the same layer with a source electrode and a drain electrode; a conductive thin film which constitutes the transmission electrode and has an area formed via an organic film on the upper layer than the first metal thin film and the second metal thin film; and the reflection electrode formed on the conductive thin film without interposing an insulation film, wherein, in the pixel part, the edge part of the reflection electrode on the area of the organic film has a part contacting with the lower layer other than the conductive thin film. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a liquid crystal display device including a pixel electrode that includes a reflective electrode that reflects external light and a transmissive electrode that transmits light from a back light source in one pixel.

  In general, in a liquid crystal display device, a liquid crystal layer made of liquid crystal is sandwiched between two substrates each having an electrode on the upper surface and the lower surface, and polarizing plates are installed on the upper and lower sides of the two substrates. The thing has the structure where the backlight was installed in the back. Surfaces having electrodes on these substrates are subjected to a so-called alignment treatment, and a director that shows the orientation of liquid crystal molecules on average is birefringent in the desired liquid crystal, and light incident from the backlight through the polarizing plate. Changes to elliptically polarized light due to birefringence and is incident on the polarizing plate on the opposite side. In this state, when a voltage is applied between the upper and lower electrodes, the alignment state of the director is changed, the birefringence of the liquid crystal layer is changed, and the elliptical polarization state incident on the opposite polarizing plate is changed. An electro-optic effect that changes the intensity and spectrum of light transmitted through the liquid crystal display device is obtained.

  In the liquid crystal display device, a backlight (back light source) is installed on the back or side, and a transmissive liquid crystal display device that displays images and a reflector on the substrate, and ambient light is reflected on the reflector surface. There is a reflective liquid crystal display device that displays an image by performing the above operation. This transmissive liquid crystal display device has a problem in that when the ambient light is very bright, the display cannot be observed because the display light is darker than the ambient light. On the other hand, the reflective liquid crystal display device has a drawback that the visibility is extremely lowered when the ambient light is dark.

In order to solve these problems, a liquid crystal display device using a transflective film that transmits part of light and reflects part of light (hereinafter referred to as a transflective liquid crystal display device) has been proposed. ing. For example, a transflective liquid crystal display device is disclosed in Patent Literature 1, Patent Literature 2, and Patent Literature 3.
JP 7-333598 A JP 2000-19563 A JP 2000-305110 A

  The conventional transflective liquid crystal display devices disclosed in these documents have a complicated manufacturing process and a low yield.

  The present invention has been made to solve such problems, and an object thereof is to provide a liquid crystal display device that realizes a high yield by a simple manufacturing process.

  A liquid crystal display device according to the present invention includes a reflective electrode that constitutes a reflective portion that reflects external light on one of a pair of substrates that are arranged to face each other with a liquid crystal layer interposed therebetween, and a back light source A liquid crystal display device comprising a pixel electrode having a transmissive electrode that constitutes a transmissive portion that transmits light from a pixel, and is formed on the one substrate and is made of the same layer as the gate electrode. A first metal thin film, a second metal thin film formed through the same layer as the source electrode and the drain electrode, and the first metal thin film and the first metal thin film. A conductive thin film constituting the transmissive electrode having a region formed above the metal thin film via an organic film, and the reflective electrode formed on the conductive thin film without an insulating film interposed therebetween. And in the pixel portion, before being in the region of the organic film End of the reflective electrode has a portion in contact with the lower layer other than the conductive thin film. According to such a liquid crystal display device, it is possible to suppress peeling between the transmissive electrode and the metal thin film.

  In the liquid crystal display device according to the present invention, in the pixel portion, the organic film is removed from the transmissive portion, and the end portion of the reflective electrode at the boundary between the transmissive portion and the reflective portion is in a region where the organic film is removed. It is characterized by being. According to such a liquid crystal display device, it is possible to suppress peeling between the transmissive electrode and the metal thin film.

  The liquid crystal display device according to the present invention is characterized in that in the pixel portion, the semiconductor film of the TFT portion remains in a continuous shape up to the lower portion of the source wiring. According to such a liquid crystal display device, disconnection of the source electrode at the stepped portion can be made difficult to occur.

  ADVANTAGE OF THE INVENTION According to this invention, the liquid crystal display device which implement | achieves a high yield with a simple manufacturing process can be provided.

Embodiment 1 of the Invention
FIG. 1 shows a manufacturing process flow of a transflective liquid crystal display device according to Embodiment 1 of the present invention. In this manufacturing process, a transflective a-Si TFT array is manufactured by seven photographic processes.

  First, a glass substrate is cleaned as an insulating substrate to clean the surface. As the insulating substrate, a transparent insulating substrate such as a glass substrate is used. The thickness of the insulating substrate may be arbitrary, but it is preferably 1.1 mm or less in order to reduce the thickness of the liquid crystal display device. If the insulating substrate is too thin, the substrate may be distorted due to various film formation and thermal history of the process, resulting in problems such as reduced patterning accuracy. Therefore, the thickness of the insulating substrate takes into account the process used. Need to choose. Further, when the insulating substrate is made of a brittle fracture material such as glass, it is preferable to chamfer the end surface of the substrate in order to prevent foreign matters from being mixed due to chipping from the end surface. In addition, it is preferable to provide a notch in a part of the insulating substrate so that the orientation of the substrate can be specified, because the direction of substrate processing in each process can be specified, thereby facilitating process management.

  Next, the first metal thin film 1 is formed by a method such as sputtering. As the first metal thin film 1, for example, a thin film having a thickness of about 100 nm to 500 nm made of any one of chromium, molybdenum, tantalum, titanium, aluminum, copper, and an alloy obtained by adding a trace amount of other substances to these is used. be able to. In the preferred embodiment, 200 nm thick chromium is used. On the first metal thin film 1, a contact hole is formed by dry etching in a process described later to form a conductive thin film. Therefore, a metal thin film that does not easily cause surface oxidation or a metal thin film that is conductive even when oxidized. Is preferably used for the first metal thin film 1, and at least the surface is preferably made of chromium, titanium, tantalum, molybdenum, or the like. Further, as the first metal thin film 1, a metal thin film in which different kinds of metal thin films are laminated or a metal thin film having a different composition in the film thickness direction can also be used. Further, when a material containing aluminum is used as the first metal thin film 1, it is preferable that at least the surface is aluminum nitride having a specific resistance of about 10 to 1000 μΩ.

  Next, the first metal thin film 1 is patterned with the gate electrode and the gate wiring, the auxiliary capacitance electrode and the auxiliary capacitance wiring in the first photolithography process (photographic process). Thereby, the structure shown in FIG. 1A is formed. In the photolithography process, after the TFT array substrate is washed, a photosensitive resist is applied and dried, then exposed through a mask pattern in which a predetermined pattern is formed, and developed to make a mask pattern on the TFT array substrate photolithography. This is performed by forming a resist to which the resist is transferred, heating and curing the photosensitive resist, etching, and peeling the photosensitive resist. If the wettability between the photosensitive resist and TFT array substrate is poor and the photosensitive resist repels, UV cleaning is performed before coating, or HMDS (hexamethyldisilazane) is used to improve wettability. Processes such as applying steam. Further, when the adhesion between the photosensitive resist and the TFT array substrate is poor and peeling occurs, the heat curing temperature is increased or the time is increased. Etching of the first metal thin film 1 is performed by wet etching using a known etchant (for example, when the first metal thin film 1 is made of chromium, an aqueous solution in which second ceric ammonium nitrate and nitric acid are mixed). It can be etched. The first metal thin film 1 is preferably etched so that the pattern edge has a tapered shape, in order to prevent a short circuit at a step with another wiring. Here, the taper shape means that the pattern edge is etched so that the cross section has a trapezoidal shape. In addition, although it has been shown that the gate electrode and the gate wiring, the auxiliary capacitance electrode and the auxiliary capacitance wiring are formed in this step, various other marks and wirings necessary for manufacturing the TFT array substrate are formed.

  Next, the first insulating film 2, the semiconductor active film 3, and the ohmic contact film 4 are continuously formed by plasma CVD. As the first insulating film 2 serving as a gate insulating film, a SiNx film, a SiOy film, a SiOzNw film, or a laminated film thereof is used (x, y, z, and w are positive numbers). The film thickness of the first insulating film 2 is about 300 nm to 600 nm. When the film thickness is small, a short circuit is likely to occur at the intersection of the gate wiring and the source wiring, and it is preferable that the thickness be about the thickness of the first metal thin film 1. When the film thickness is large, the ON current of the TFT becomes small and the display characteristics are deteriorated. In a preferred embodiment, a first insulating film 2 is formed by forming a 300 nm SiN film and then forming a 100 nm SiN film.

  As the semiconductor active film 3, an amorphous silicon (a-Si) film or a polysilicon (p-Si) film is used. The film thickness of the semiconductor active film 3 is about 100 nm to 300 nm. When the film thickness is thin, the ohmic contact film 4 to be described later disappears during dry etching. When the film thickness is thick, the ON current of the TFT is reduced, so that the etching depth of the ohmic contact film 4 during dry etching is reduced. The film thickness is selected based on the controllability and the required ON current of the TFT. When an a-Si film is used as the semiconductor active film 3, the interface between the first insulating film 2 and the a-Si film is a SiNx film or a SiOzNw film. It is preferable in terms of controllability and reliability of Vth. When a p-Si film is used as the semiconductor active film 3, it is preferable that the interface between the first insulating film 2 and the p-Si film is a SiOy film or a SiOzNw film in terms of controllability and reliability of Vth of the TFT. When an a-Si film is used as the semiconductor active film 3, the vicinity of the interface with the first insulating film 2 is formed under a condition with a low film formation rate, and the upper layer is formed under a condition with a high film formation rate. It is more preferable that TFT characteristics with high mobility can be obtained in a short film formation time and that the leakage current when the TFT is turned off can be reduced. In a preferred embodiment, a 150 nm ia-Si film is formed as the semiconductor active film 3.

  As the ohmic contact film 4, an na-Si film or an np-Si film obtained by doping a-Si with a small amount of phosphorus (P) is used. The thickness of the ohmic contact film 4 can be about 20 nm to 70 nm. These SiNx film, SiOy film, SiOzNw film, a-Si film, p-Si film, na-Si film, and np-Si film are known gases (SiH4, NH3, H2, NO2, PH3, N2 And a mixed gas thereof). In a preferred embodiment, a 30 nm na-Si film is deposited as the ohmic contact film 4.

  Next, the semiconductor active film 3 and the ohmic contact film 4 are patterned at least in a portion where the TFT portion is formed by a second photolithography process. As a result, the structure shown in FIG. 1B is formed. The first insulating film 2 remains throughout. The semiconductor active film 3 and the ohmic contact film 4 can be left by patterning and remaining in a portion where the source wiring, the gate wiring, and the auxiliary capacitance wiring cross in a plane in addition to the portion where the TFT portion is formed. It is more preferable that the withstand voltage becomes larger. In addition, the semiconductor active film 3 and the ohmic contact film 4 in the TFT portion remain in a continuous shape up to the lower portion of the source wiring, so that the source electrode does not extend over the step between the semiconductor active film 3 and the ohmic contact film 4. This is preferable because disconnection of the source electrode is difficult to occur.

The semiconductor active film 3 and the ohmic contact film 4 can be etched by a known gas composition (for example, a mixed gas of SF ₆ and O ₂ or a mixed gas of CF ₄ and O ₂ ).

  Next, a second metal thin film is formed by a method such as sputtering. As the second metal thin film, for example, chromium, molybdenum, tantalum, titanium, aluminum, copper, an alloy obtained by adding a small amount of other substances to these, or a laminated film thereof is used. In a preferred embodiment, chromium having a thickness of 200 nm is deposited.

Next, the second metal thin film is patterned by the third photolithography process so as to form the source electrode 5 and the drain electrode 6. Thereby, the structure shown in FIG. 1C is formed. The source electrode 5 is formed over a portion where the source wiring and the gate wiring intersect. The drain electrode 6 is formed over the reflection portion. Next, the ohmic contact film 4 is etched. By this process, the central portion of the ohmic contact film 4 in the TFT portion is removed, and the semiconductor active film 3 is exposed. The ohmic contact film 4 can be etched by a known gas composition (for example, a mixed gas of SF ₆ and O ₂ or a mixed gas of CF ₄ and O ₂ ).

  Next, the second insulating film 7 and the organic film 8 are formed by plasma CVD. In a preferred embodiment, SiN having a thickness of 100 nm is used as the second insulating film 7. The organic film 8 is a known photosensitive organic film, and for example, J335 PC335 or PC405 is used.

  Next, the organic film 8 is patterned into the shape shown in FIG. 1D by a fourth photolithography process. Specifically, the organic film 8 is formed so that the first and second insulating films 2 and 7 are exposed in a portion where the first and second insulating films 2 and 7 are removed by the subsequent fifth photolithography process. Pattern. In addition, the reflection part also forms a portion where the organic film 8 is removed and a portion where the organic film 8 is not removed, thereby forming an uneven shape.

  Next, the organic film is patterned by a fifth photolithography process. At this time, the portion of the organic film from which the first and second insulating films 2 and 7 are removed is removed. In addition, the organic film in the uneven portion is not removed, and good scattering characteristics can be obtained by moderately reducing the unevenness in the first layer. Subsequently, taper etching is performed to form the structure of FIG. That is, in the gate terminal portion, both the first insulating film 2 and the second insulating film 7 are removed to form a contact hole for electrically connecting the gate wiring and the drive signal source, and the first metal is removed. The thin film 1 is exposed. In the source terminal portion, the second insulating film 7 is removed and the second metal thin film is exposed. Between the TFT portion and the reflective portion, the second insulating film is removed and the drain electrode 6 is exposed. Further, in the transmission part, both the first insulating film and the second insulating film are removed, and the first insulating substrate is exposed.

  Next, the conductive thin film 9 is formed by a method such as sputtering. As the conductive thin film 9, ITO, SnO2, etc. which are transparent conductive films can be used, and ITO is particularly preferable from the viewpoint of chemical stability. In a preferred embodiment, the conductive thin film 9 is made of ITO having a thickness of 80 nm. The ITO may be either crystallized ITO or amorphous ITO, but when amorphous ITO is used, it is necessary to heat and crystallize to a crystallization temperature of 180 ° C. or higher before forming the third metal thin film. . In a preferred embodiment, heating to 200 ° C. or higher.

  Next, the conductive thin film 9 is patterned into a shape of a pixel electrode or the like as shown in FIG. 1F by a sixth photolithography process. The conductive thin film 9 can be etched using known wet etching (for example, an aqueous solution in which hydrochloric acid and nitric acid are mixed when the conductive thin film 9 is made of crystallized ITO) depending on the material used. is there. When the conductive thin film 9 is ITO, etching by dry etching with a known gas composition (for example, HI, HBr) is also possible. In addition, although it has been shown that the pixel electrode is formed in this step, the conductive thin film 9 in the transfer terminal portion for electrically connecting the counter substrate and the TFT array substrate using a resin containing conductive particles. The electrode etc. by are formed. In the case of amorphous ITO, patterning is performed with an aqueous solution in which a known oxalic acid is mixed before heating, similarly to ITO if heated.

  Next, the third metal thin films 10 and 11 are formed by a method such as sputtering. As the third metal thin films 10 and 11, for example, chromium, molybdenum, tantalum, titanium, aluminum, copper, or an alloy obtained by adding a trace amount of other substances to these, a film thickness of about 100 nm to 500 nm. The thin film can be used. The metal thin film 10 has an effect of preventing the metal thin film 11 from being cut off at a step such as a contact hole portion. If this step break is negligible, the metal thin film 10 may not be formed. In this case, the number of processes is reduced, and the cost can be reduced. In a preferred embodiment, after depositing chromium having a thickness of 100 nm, an alloy of aluminum and Cu having a thickness of 300 nm is deposited, and further chromium having a thickness of 100 nm is deposited. If the alloy of aluminum and Cu is exposed, the corrosion of the ITO 9 proceeds during development in the next photographic process. To prevent this, chromium is provided in the uppermost layer.

  Next, in the seventh photolithography process, the third metal thin films 10 and 11 and the uppermost chromium layer are patterned into the shape of the reflective electrode, and the uppermost chromium layer is removed by etching to form the reflective electrode. In addition, when the metal film 10 is chromium, it is also possible to etch simultaneously with the uppermost chromium. The reflective electrode is formed in a state where a metal thin film 11 made of an alloy of aluminum and Cu is laminated on a metal thin film 10 made of chromium. The uppermost chromium layer is provided to prevent corrosion of the ITO 9, but is removed at this stage to increase the reflectivity. The etching of the third metal thin film can be performed by wet etching using a known etchant. Finally, the structure shown in FIG. 1G is formed. As described above, the liquid crystal display device according to the embodiment of the present invention is characterized in that the reflective electrodes 10 and 11 and the conductive thin film 9 are provided without an insulating layer interposed therebetween.

  Through the above steps, the TFT array substrate is manufactured by a seven-step photolithography process, and the yield can be increased. In the first embodiment of the present invention, the third metal thin films 10 and 11 are provided in two layers. However, the present invention is not limited to this, and as shown in FIG. Good. In Embodiments 2, 3, and 4 of the following invention, an example in which only the third metal thin film 11 is formed as one layer will be described. Further, by using a developer having an effect of inhibiting corrosion of ITO such as ELM-DSA manufactured by Mitsubishi Chemical in the photographic process of the metal thin film 10 or 11, it contains any one of the uppermost metals, that is, molybdenum, tantalum, and tungsten. No metal is required. In this case, the number of processes can be reduced. In the following embodiment, an example in which chromium is provided in the uppermost layer will be described.

Reference form of the invention
FIG. 2 shows a manufacturing process flow of the transflective liquid crystal display device according to the second embodiment of the present invention. In this manufacturing process, a transflective a-Si TFT array is manufactured by six photographic processes.

  First, a 0.7 mm thick glass substrate is cleaned as an insulating substrate to clean the surface. Since the insulating substrate is the same as that described in the first embodiment of the present invention, the description thereof is omitted.

  Next, the first metal thin film 1 is formed by a method such as sputtering. As the first metal thin film 1, for example, a thin film having a thickness of about 100 nm to 500 nm made of any one of chromium, molybdenum, tantalum, titanium, aluminum, copper, and an alloy obtained by adding a trace amount of other substances to these is used. be able to. In the preferred embodiment, 200 nm thick chromium is used. Since the first metal thin film 1 is the same as that described in the first embodiment of the present invention, the description thereof is omitted.

  Next, the first metal thin film 1 is patterned into the gate electrode and the gate wiring, the auxiliary capacitance electrode, and the auxiliary capacitance wiring by the first photolithography process. As a result, the structure shown in FIG. 2A is formed. Since the manufacturing method of this structure is the same as that of the first embodiment of the present invention, the description thereof is omitted.

  Next, the first insulating film 2, the semiconductor active film 3, the ohmic contact film 4, and the second metal thin film are successively formed. In a preferred embodiment, a laminated film of 300 nm SiN and 100 nm SiN is used as the first insulating film 2 serving as a gate insulating film. As the semiconductor active film 3, a 150 nm ia-Si film is used. Furthermore, a 30 nm na-Si film is used as the ohmic contact film 4. As the second metal thin film, 200 nm of chromium is used. These SiN film, a-Si film, and na-Si film are formed using a plasma CVD apparatus, and at the time of ohmic film formation, PH3 is doped to form an na-Si film. Regarding the Cr film formation, for example, the film is formed using a DC magnetron type sputtering apparatus.

  Next, a resist pattern for forming the source wiring, the source terminal portion metal pad, the drain electrode, the semiconductor active film 3 and the like is formed by a second photolithography process. In the second photolithography process, halftone exposure is used.

  Here, halftone exposure will be described with reference to FIGS. In the halftone exposure, for example, a mask as shown in FIG. 5 is used. In this mask, the spatial frequency of the exposure pattern on the mask is made higher than the pattern resolution capability of the exposure machine (for example, 1.6 μm), the mask pattern cannot be resolved on the photoresist, and the exposure intensity is adjusted. is there. Light is irradiated through this mask, and the remaining film thickness of the photoresist can be controlled by controlling the amount of the irradiated light. That is, as shown in FIG. 6, when the light amount is adjusted within the range of the light amount that disappears by development, the remaining film thickness of the photoresist changes accordingly. Specifically, a smaller amount of photoresist remains in a place where the amount of light is large, and a larger amount of photoresist remains in a place where the amount of light is small.

  In this example, a novolac resin-based positive resist is used as the resist, and the resist coating is 1.5 μm by a spin coater. After applying the resist, pre-baking is performed at 120 ° C. for 90 seconds. Thereafter, the resist pattern is a normal Cr entire surface mask pattern, and the resist pattern is a half having a Cr stripe shape of line / space = 1.5 μm / 1.5 μm. The exposure was performed for 1000 msec using a tone mask pattern. The exposure machine is a normal stepper or mirror projection type exposure machine, and the light source uses g-line and h-line of a high-pressure mercury lamp. At this time, since the stripe pattern is a pattern finer than the resolution limit of the exposure apparatus, the resist is not exposed in a stripe shape, and the average exposure amount is smaller than that of other exposure portions.

Next, after developing using an organic alkaline developer, post-baking is performed at 100 ° C. to 120 ° C. for 180 seconds to volatilize the solvent in the resist and simultaneously increase the adhesion between the resist and Cr. Thereafter, oven baking is further performed at 120 to 130 ° C., and the adhesion between the resist and Cr is further increased. At this time, if the baking temperature is too high, the end face of the resist will be bent. Thereafter, etching of the Cr film is performed using (NH ₄ ) 2 [Ce (NO ₃ ) ₆ ] + HNO ₃ + H ₂ O solution. Thereafter, the ohmic contact film 4 and the semiconductor active film 3 are etched using HCl + SF ₆ gas. Thereafter, the resist is ashed by oxygen plasma so that the Cr film in the resist pattern portion is exposed. Ashing was performed at a pressure of 40 Pa for 60 seconds. In ashing, the size of the resist opening is easier to control in the RIE mode than in the PE mode. In this way, the structure shown in FIG. 2B is formed.

  Then, after baking at 130 to 140 ° C., the Cr film is etched using (NH 4) 2 [Ce (NO 3) 6] + HNO 3 + H 2 O solution. Next, the ohmic contact film is removed.

  Next, a second insulating film 7 is formed by plasma CVD. Next, the organic film 8 is patterned into the shape shown in FIG. 2C by a third photolithography process. Specifically, the organic film 8 is formed so that the first and second insulating films 2 and 7 are exposed at a portion where the first and second insulating films 2 and 7 are removed by the subsequent fourth photolithography process. Pattern. In addition, the reflection part also forms a portion where the organic film 8 is removed and a portion where the organic film 8 is not removed, thereby forming an uneven shape.

  Next, the organic film is patterned by a fourth photolithography process. At this time, the portion of the organic film from which the first and second insulating films 2 and 7 are removed is removed. In addition, the organic film in the uneven portion is not removed, and good scattering characteristics can be obtained by moderately reducing the unevenness in the first layer. Subsequently, taper etching is performed to form the structure of FIG. That is, in the gate terminal portion, both the first insulating film 2 and the second insulating film 7 are removed to form a contact hole for electrically connecting the gate wiring and the drive signal source, and the first metal is removed. The thin film 1 is exposed. In the source terminal portion, the second insulating film 7 is removed and the second metal thin film is exposed. Between the TFT portion and the reflective portion, the second insulating film is removed and the drain electrode 6 is exposed. Further, in the transmission part, both the first insulating film and the second insulating film are removed, and the first insulating substrate is exposed.

  Next, the conductive thin film 9 is formed by a method such as sputtering. In a preferred embodiment, the conductive thin film 9 is made of ITO having a thickness of 80 nm. The ITO may be either crystallized ITO or amorphous ITO, but when amorphous ITO is used, it is necessary to heat and crystallize to a crystallization temperature of 180 ° C. or higher before forming the third metal thin film. . In a preferred embodiment, heating to 200 ° C. or higher.

  Next, the conductive thin film 9 is patterned into a shape such as a pixel electrode as shown in FIG. 2E by a fifth photolithography process. The conductive thin film 9 can be etched using known wet etching (for example, an aqueous solution in which hydrochloric acid and nitric acid are mixed when the conductive thin film 9 is made of crystallized ITO) depending on the material used. is there. When the conductive thin film 9 is ITO, etching by dry etching with a known gas composition (for example, HI, HBr) is also possible. In addition, although it has been shown that the pixel electrode is formed in this step, the conductive thin film 9 in the transfer terminal portion for electrically connecting the counter substrate and the TFT array substrate using a resin containing conductive particles. The electrode etc. by are formed. In the case of amorphous ITO, patterning is performed with an aqueous solution in which a known oxalic acid is mixed before heating, similarly to ITO if heated.

  Next, the third metal thin film 11 is formed by a method such as sputtering. As the third metal thin film 11, for example, a thin film having a thickness of about 100 nm to 500 nm made of any one of chromium, molybdenum, tantalum, titanium, aluminum, copper and an alloy obtained by adding a small amount of other substances to these. Can be used. In a preferred embodiment, an alloy of aluminum and Cu having a thickness of 300 nm is formed, and chromium having a thickness of 100 nm is further formed. If the alloy of aluminum and Cu is exposed, the corrosion of the ITO 9 proceeds during development in the next photographic process. To prevent this, chromium is provided in the uppermost layer.

  Next, in the sixth photolithography process, the third metal thin film 11 and the uppermost chromium layer are patterned into the shape of the reflective electrode, and the uppermost chromium layer is removed by etching to form the reflective electrode. In addition, when the metal film 11 is chromium, it is also possible to etch simultaneously with the uppermost chromium. The uppermost chromium layer is provided to prevent corrosion of the ITO 9, but is removed at this stage to increase the reflectivity. The etching of the third metal thin film can be performed by wet etching using a known etchant. Finally, the structure shown in FIG. 2 (f) is formed. As described above, the liquid crystal display device according to the embodiment of the present invention is characterized in that the reflective electrode 11 and the conductive thin film 9 are provided without an insulating layer interposed therebetween.

  Through the above steps, the TFT array substrate is manufactured by a six-step photolithography process, and the yield can be increased.

2. Reference form of the invention
FIG. 3 shows a manufacturing process flow of the transflective liquid crystal display device according to the third embodiment of the present invention. In this manufacturing process, a transflective a-Si TFT array is manufactured using six masks.

  First, a 0.7 mm thick glass substrate is cleaned as an insulating substrate to clean the surface. Since the insulating substrate is the same as that described in the first embodiment of the present invention, the description thereof is omitted.

  Next, the first metal thin film 1 is formed by a method such as sputtering. As the first metal thin film 1, for example, a thin film having a thickness of about 100 nm to 500 nm made of any one of chromium, molybdenum, tantalum, titanium, aluminum, copper, and an alloy obtained by adding a trace amount of other substances to these is used. be able to. In the preferred embodiment, 200 nm thick chromium is used. Since the first metal thin film 1 is the same as that described in the first embodiment of the present invention, the description thereof is omitted.

  Next, the first metal thin film 1 is patterned into the gate electrode 1 and the gate wiring, the auxiliary capacitance electrode 2 and the auxiliary capacitance wiring by the first photolithography process. As a result, the structure shown in FIG. 3A is formed. Since the manufacturing method of this structure is the same as that of the first embodiment of the present invention, the description thereof is omitted.

  Next, the first insulating film 2, the semiconductor active film 3, and the ohmic contact film 4 are continuously formed by plasma CVD. Thereafter, the structure shown in FIG. 3B is formed by etching or the like. Since this manufacturing method is the same as that in the first embodiment of the present invention, the description thereof is omitted.

  Next, a second metal thin film is formed by a method such as sputtering. For example, chromium is used as the first metal thin film 1. In a preferred embodiment, chromium having a thickness of 200 nm is deposited.

Next, the second metal thin film is patterned by the third photolithography process so as to form the source electrode 5 and the drain electrode 6. Thereby, the structure shown in FIG. 3C is formed. The source electrode 5 is formed over a portion where the source wiring and the gate wiring intersect. The drain electrode 6 is formed over the reflection portion. By this process, the central portion of the ohmic contact film 4 in the TFT portion is removed, and the semiconductor active film 3 is exposed. The ohmic contact film 4 can be etched by a known gas composition (for example, a mixed gas of SF ₆ and O ₂ or a mixed gas of CF ₄ and O ₂ ).

  Next, the second insulating film 7 and the organic film 8 are formed by plasma CVD. In a preferred embodiment, SiN having a thickness of 100 nm is used as the second insulating film 7. The organic film 8 is a known photosensitive organic film, for example, J335 PC335 or PC405 is used.

  Next, patterning is performed in a shape shown in FIG. 3D by a fourth photolithography process. In the fourth photolithography process, halftone exposure is used. The halftone exposure is as described in the second embodiment of the invention. By this halftone exposure and the next etching, the organic film in the contact hole portion that electrically connects the gate wiring and the drive signal source is removed from the gate terminal portion, and the first insulating film 2 and the second etching are performed by the next etching. Both of the two insulating films 7 are removed, and the first metal thin film 1 is exposed. In the source terminal portion, the second insulating film 7 is removed and the second metal thin film is exposed. Between the TFT portion and the reflective portion, the second insulating film is removed and the drain electrode 6 is exposed. Further, in the transmission part, both the first insulating film and the second insulating film are removed, and the first insulating substrate is exposed. In addition, since the organic film remains in the concave portion of the concavo-convex portion, the second insulating film is not removed, and the concavo-convex portion by the organic film is formed.

Next, the conductive thin film 9 is formed by a method such as sputtering. As the conductive thin film 9, ITO, SnO _2, etc., which are transparent conductive films, can be used when the liquid crystal display device is configured as a transmission type, and ITO is particularly preferable from the viewpoint of chemical stability. In a preferred embodiment, the conductive thin film 9 is made of ITO having a thickness of 80 nm. In addition, ITO may be either crystallized ITO or amorphous ITO. However, when amorphous ITO is used, it is necessary to heat and crystallize to a crystallization temperature of 180 ° C. or higher before forming the third metal thin film. . In a preferred embodiment, heating to 200 ° C. or higher.

  Next, the conductive thin film 9 is patterned into a shape such as a pixel electrode as shown in FIG. 3E by a fifth photolithography process. The conductive thin film 9 can be etched using known wet etching (for example, an aqueous solution in which hydrochloric acid and nitric acid are mixed when the conductive thin film 9 is made of crystallized ITO) depending on the material used. is there. When the conductive thin film 9 is ITO, etching by dry etching with a known gas composition (for example, HI, HBr) is also possible. In addition, although it has been shown that the pixel electrode is formed in this step, the conductive thin film 9 in the transfer terminal portion for electrically connecting the counter substrate and the TFT array substrate using a resin containing conductive particles. The electrode etc. by are formed. In the case of amorphous ITO, patterning is performed with an aqueous solution in which a known oxalic acid is mixed before heating, similarly to ITO if heated.

  Next, the third metal thin film 11 is formed by a method such as sputtering. As the third metal thin film, for example, a thin film having a thickness of about 100 nm to 500 nm made of any one of chromium, molybdenum, tantalum, titanium, aluminum, copper, and an alloy obtained by adding a trace amount of other substances to these. Can be used. In a preferred embodiment, after depositing chromium having a thickness of 100 nm, an alloy of aluminum and Cu having a thickness of 300 nm is deposited, and further chromium having a thickness of 100 nm is deposited. If the alloy of aluminum and Cu is exposed, the corrosion of the ITO 9 proceeds during development in the next photographic process. To prevent this, chromium is provided in the uppermost layer.

  Next, the third metal thin film 11 and the uppermost chromium layer are patterned into the shape of the reflective electrode by a sixth photolithography process to form the reflective electrode. In addition, when the metal film 11 is chromium, it is also possible to etch simultaneously with the uppermost chromium. Etching of the third metal thin film 11 can be performed by wet etching using a known etchant. Finally, the structure shown in FIG. 3F is formed. As described above, the liquid crystal display device according to the embodiment of the present invention is characterized in that the reflective electrode 11 and the conductive thin film 9 are provided without an insulating layer interposed therebetween.

  Through the above steps, the TFT array substrate is manufactured by a six-step photolithography process, and the yield can be increased.

3. Reference form of the invention
FIG. 4 shows a manufacturing process flow of the transflective liquid crystal display device according to the fourth embodiment of the present invention. In this manufacturing process, a transflective a-Si TFT array is manufactured using five photographic processes.

  First, a 0.7 mm thick glass substrate is cleaned as an insulating substrate to clean the surface. Since the insulating substrate is the same as that described in the first embodiment of the present invention, the description thereof is omitted.

  Next, the first metal thin film 1 is formed by a method such as sputtering. As the first metal thin film 1, for example, a thin film having a thickness of about 100 nm to 500 nm made of any one of chromium, molybdenum, tantalum, titanium, aluminum, copper, and an alloy obtained by adding a trace amount of other substances to these is used. be able to. In the preferred embodiment, 200 nm thick chromium is used. Since the first metal thin film 1 is the same as that described in the first embodiment of the present invention, the description thereof is omitted.

  Next, the first metal thin film 1 is patterned into the gate electrode 1 and the gate wiring, the auxiliary capacitance electrode 2 and the auxiliary capacitance wiring by the first photolithography process. Thereby, the structure shown in FIG. 4A is formed. Since the manufacturing method of this structure is the same as that of the first embodiment of the present invention, the description thereof is omitted.

Next, the first insulating film 2, the semiconductor active film 3, the ohmic contact film 4, and the second metal thin film are successively formed. In a preferred embodiment, a laminated film of 300 nm SiN and 100 nm SiN is used as the first insulating film to be the gate insulating film 2. As the semiconductor active film 3, a 150 nm ia-Si film is used. Furthermore, a 30 nm na-Si film is used as the ohmic contact film 4. As the second metal thin film, 200 nm of chromium is used. These SiN film, a-Si film, and na-Si film are formed using a plasma CVD apparatus, and at the time of ohmic film formation, PH ₃ is doped to form an na-Si film. Regarding the Cr film formation, for example, the film is formed using a DC magnetron type sputtering apparatus.

  Next, a resist pattern for forming the source wiring, the source terminal portion metal pad, the drain electrode, the semiconductor active film 3 and the like is formed by a second photolithography process. In the second photolithography process, halftone exposure is used. Halftone exposure is as described in the second embodiment of the invention. Further, since this step is also as described in the second embodiment of the invention, the description thereof is omitted. In this way, the structure shown in FIG. 4B is formed.

Then, after baking at 130 to 140 ° C., the Cr film is etched using (NH ₄ ) 2 [Ce (NO ₃ ) ₆ ] + HNO ₃ + H ₂ O solution.

  Next, the second insulating film 7 and the organic film 8 are formed by plasma CVD. In a preferred embodiment, SiN having a thickness of 100 nm is used as the second insulating film 7. The organic film 8 is a known photosensitive organic film, for example, J335 PC335 or PC405 is used.

  Next, patterning is performed in a shape shown in FIG. 4C by a third photolithography process. In the third photolithography process, halftone exposure is used. This step is as described in the third embodiment of the present invention, and the description is omitted.

Next, the conductive thin film 9 is formed by a method such as sputtering. As the conductive thin film 9, ITO, SnO _2, etc., which are transparent conductive films, can be used when the liquid crystal display device is configured as a transmission type, and ITO is particularly preferable from the viewpoint of chemical stability. In a preferred embodiment, the conductive thin film 9 is made of ITO having a thickness of 80 nm.

  Next, the conductive thin film 9 is patterned into a shape such as a pixel electrode as shown in FIG. 4D by a fourth photolithography process. This step is as described in the third embodiment of the present invention, and the description is omitted.

  Next, the third metal thin film 11 is formed by a method such as sputtering. This process is also as described in the third embodiment of the present invention, and the description is omitted. Further, the third metal thin film 11 is patterned into the shape of the reflective electrode by the fifth photolithography process to form the reflective electrode. Ultimately, the structure shown in FIG. 4E is formed. As described above, the liquid crystal display device according to the embodiment of the present invention is characterized in that the reflective electrode 11 and the conductive thin film 9 are provided without an insulating layer interposed therebetween.

  Through the above steps, the TFT array substrate is manufactured by a five-step photolithography process, and the yield can be increased.

Embodiment 5 of the Invention
FIG. 8 shows the configuration of a transflective liquid crystal display device according to Embodiment 5 of the present invention. This configuration can be realized in any of the first to fourth embodiments, but this embodiment shows an example formed by the process flow shown in the first embodiment.

  In the liquid crystal display device according to the embodiment of the present invention, the connection portion between the first or second metal thin film and the transmissive electrode (conductive thin film 9), that is, the contact hole portion provided in the first or second insulating film. At least a part of the transmissive electrode is removed, and this part is covered with the third metal thin film 10 or 11. At this time, the third metal thin films 10 and 11 are connected to both the conductive thin film 9 and the first or second metal thin film. Such a configuration has the following effects. Generally, the connection resistance between the transmissive electrode and the metal thin film through the contact hole is higher than the connection resistance between the metal thin film and the metal thin film through the contact hole. Therefore, the connection resistance between the transmissive electrode and the first or second metal thin film can be reduced with the above configuration.

  With the above configuration, the connection resistance between each wiring and the transmissive electrode in the TFT array substrate can be reduced, display defects caused by an increase in the connection resistance can be suppressed, and the yield can be increased.

Embodiment 6 of the Invention
FIG. 9 shows the configuration of a transflective liquid crystal display device according to Embodiment 6 of the present invention. This configuration can be realized in any of the first to fourth embodiments, but in the sixth embodiment, an example formed by the process flow of the first embodiment will be described.

The liquid crystal display device according to the embodiment of the present invention is characterized in that the transmissive electrode (conductive thin film 9) on the organic film is included by the third metal thin films 10 and 11 in the pixel portion.
Such a configuration has the following effects. Generally, the adhesion between a transmissive electrode (conductive thin film 9) formed on an organic film and a metal thin film formed on the transmissive electrode without an insulating film is a metal formed directly on the organic film. The problem arises that the metal thin film formed on the transmissive electrode on the organic film and the transmissive electrode is peeled off during the subsequent manufacturing process. In response to this problem, peeling of the metal thin film is remarkably improved by adopting the configuration of the present embodiment. As a preferred example, a configuration in which the transmissive electrode is included within 1 μm or more inside the metal thin film is preferable. Note that the adhesion between the transmissive electrode on the insulating substrate and the metal thin film is good, and there is no problem of peeling between the transmissive electrode and the metal thin film at the opening of the transmissive portion.

  With the above configuration, peeling of the transmissive electrode and the third metal thin film on the TFT array substrate can be suppressed, and the yield can be increased.

It is a figure which shows the process flow of the liquid crystal display device concerning Embodiment 1 of this invention. It is a figure which shows the process flow of the liquid crystal display device concerning Embodiment 2 of this invention. It is a figure which shows the process flow of the liquid crystal display device concerning Embodiment 3 of this invention. It is a figure which shows the process flow of the liquid crystal display device concerning Embodiment 4 of this invention. It is a principle figure in the case of forming unevenness by coating, exposing and developing an organic film. It is a figure which shows the structural example of the halftone mask used in this invention. It is a figure which shows the process flow of the liquid crystal display device concerning other embodiment. It is sectional drawing of the liquid crystal display device concerning Embodiment 5 of this invention. It is sectional drawing of the liquid crystal display device concerning Embodiment 6 of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 1st metal thin film 2 1st insulating film 3 Semiconductor active film 4 Ohmic contact film 5 Source electrode 6 Drain electrode 7 2nd insulating film 8 Organic film 9 Conductive thin film 10,11 3rd metal thin film

Claims (3)

A reflective electrode that constitutes a reflective part that reflects external light on one of a pair of substrates disposed opposite to each other with a liquid crystal layer interposed therebetween;
A liquid crystal display device comprising a pixel electrode that constitutes a transmissive electrode that constitutes a transmissive portion that transmits light from a rear light source in one pixel,
A first metal thin film formed on the one substrate and made of the same layer as the gate electrode;
A second metal thin film formed through the first metal thin film and the first insulating film and comprising the same layer as the source electrode and the drain electrode;
A conductive thin film constituting the transmissive electrode having a region formed via an organic film in an upper layer than the first metal thin film and the second metal thin film;
The reflective electrode formed without an insulating film on the conductive thin film,
In the pixel portion, a liquid crystal display device, wherein an end portion of the reflective electrode in the region of the organic film has a portion in contact with a lower layer other than the conductive thin film.   2. The pixel portion according to claim 1, wherein an organic film is removed from the transmissive portion, and an end portion of the reflective electrode at a boundary between the transmissive portion and the reflective portion is in a region where the organic film is removed. The liquid crystal display device described.   3. The liquid crystal display device according to claim 1, wherein in the pixel portion, the semiconductor film of the TFT portion remains in a continuous shape up to the lower portion of the source wiring.

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