JP4115761B2 - Active matrix substrate, method for manufacturing the same, and display device using the same - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an active matrix substrate suitable for use in a liquid crystal display device and the like, a method for manufacturing the same, and a display device using the same.
[0002]
[Prior art]
In recent years, in the field of display devices, active matrix display devices that can obtain high display quality have been widely used. In this active matrix type display device, a switching element is provided for each of a large number of pixel electrodes arranged in a matrix on a substrate, and characteristics such as an increase in size and a higher definition can be obtained by reliable switching. Can be easily obtained.
[0003]
In such a display device, it is required to further increase the display brightness by making the pixel region as large as possible. For this reason, a device in which a thick insulating film is formed on the entire surface of the active matrix substrate and a pixel electrode is formed on the insulating film has been put into practical use. In such a structure in which the pixel electrode is placed on the insulating film, an electrical short circuit occurs between the scanning line, the signal line, etc. arranged in the lower layer of the insulating film and the pixel electrode arranged in the upper layer. Therefore, the pixel electrode can be formed in a wide area so as to overlap these wirings. As a result, all regions other than regions where switching elements such as thin film transistors (hereinafter abbreviated as TFTs), scanning lines, and signal lines are formed can be pixel regions, and the aperture ratio can be improved. Further, when used in a liquid crystal display device, the step structure of the TFT, the scanning line, and the signal line portion is flattened by the thick insulating film, so that the display defect due to the alignment disorder of the liquid crystal molecules generated in the step portion is eliminated. There are also advantages that can be made.
[0004]
Conventionally, a silicon-based inorganic insulating film formed by CVD has been used as such an insulating film. However, when a thick film is formed by CVD, it takes too much time to form a silicon-based insulating film. The dielectric constant is high, and a large parasitic capacitance is generated between the pixel electrode. For this reason, organic insulating films that have a low dielectric constant, can be formed relatively uniformly in a short time by printing or spin coating, and are advantageous in terms of cost are widely used.
[0005]
By the way, in the structure in which the pixel electrode is placed on the insulating film as described above, the contact between the source electrode of the TFT and the pixel electrode is made through a contact hole penetrating the insulating film in the film thickness direction.
This contact hole is formed by etching. At this time, if there is an etching residue or a natural oxide film on the surface of the source electrode, the contact resistance is deteriorated, resulting in the occurrence of a display defect and a decrease in reliability. For this reason, plasma cleaning (or reverse sputtering) or the like is performed to remove such etching residues on the surface of the source electrode, natural oxide film, and the like, and then the pixel electrode is formed.
[0006]
[Problems to be solved by the invention]
However, when plasma cleaning is performed, the organic film surface may be carbonized due to plasma damage, and an altered layer may be formed on the organic film surface. Since this altered layer has a reduced surface resistance due to carbonization, there is a possibility that the insulating property of the organic film surface is deteriorated and a leak current is generated between the pixel electrodes due to the altered low-resistance altered layer interposed between the pixel electrodes. For this reason, when a display device is configured using such a substrate, the display contrast may be reduced.
[0007]
FIG. 12 shows the relationship between the leakage current between the pixel electrodes and the contrast in the transmissive liquid crystal display device, and FIG. 13 shows the relationship between the plasma cleaning power and the surface resistance and contact resistance of the organic film. As shown in FIG. 12, the contrast has a leakage current of 10^-12When it exceeds A, it begins to fall gradually.^-10When A is exceeded, it turns out that it falls rapidly. Therefore, in order to stabilize the display, the leak current is set to 10^-12It is preferable to suppress it to A or less. In this case, it is considered preferable to suppress the plasma cleaning power to 100 W or less (see FIG. 13A). Conversely, if the plasma cleaning power is suppressed to 100 W or less, the contact between the pixel electrode and the source electrode is reduced. Resistance is 10²As shown in FIG. 13B, there is a possibility that a good contact cannot be obtained.
[0008]
In order to avoid such a problem, for example, a method of performing plasma cleaning after forming a protective film on the organic insulating film is conceivable. However, in this case, the number of steps of forming the protective film and patterning increase, which leads to a decrease in productivity and an increase in cost.
In addition, dry etching using a special gas that reduces damage to the organic insulating film or plasma cleaning using a special organic material with little deterioration can be considered. The selection and selection of appropriate materials and process conditions may reduce the degree of freedom of the process and impair productivity and reliability.
[0009]
The present invention has been made in view of the above-described problems, and an object thereof is to provide an active matrix substrate and a display device using the same, which can prevent current leakage between pixel electrodes.
Another object of the present invention is to provide a method for manufacturing an active matrix substrate that can prevent current leakage between pixel electrodes without impairing the degree of freedom of the process.
[0010]
[Means for Solving the Problems]
In order to achieve the above object, an active matrix substrate according to the present invention includes a substrate, a scanning line provided on the substrate, a signal line provided on the substrate so as to intersect the scanning line, A switching element provided in the vicinity of the intersection of the scanning line and the signal line, and a contact hole that is formed on the substrate so as to cover the scanning line, the signal line, and the switching element, and communicates with the switching element. An organic insulating layer; and a pixel electrode formed on the organic insulating layer and electrically connected to the switching element through the contact hole.at leastIn the region where the pixel electrode is not formed, the organic insulating layerRemove surface layerdo itDirect alignment film on the underlying portion of the organic insulating layer exposedIt is characterized by the formation.
[0011]
According to this configuration, the recess in which the base portion of the organic insulating layer having a high surface resistance is exposed around the pixel electrode.(Exposed portion of the organic insulating layer underlayer)Therefore, the pixel electrodes adjacent to each other can be well insulated with respect to surface conduction by such a high resistance region. Thereby, current leakage between the pixel electrodes via the organic insulating layer can be prevented.
At this time,The exposed portion of the organic insulation layerSurface resistance of 1 × 10¹³It is desirable that it is Ω or more. According to this configuration, when the active matrix substrate is applied to a transmissive liquid crystal display device, the display contrast can be set to 300 or more.
[0013]
The display device of the present invention is held between the active matrix substrate, a counter substrate having a counter electrode provided to face a pixel electrode of the active matrix substrate, and the active matrix substrate and the counter substrate. And a light modulation layer.
In this configuration, since the active matrix substrate that can prevent current leakage between the pixel electrodes is used, a high-definition display with high contrast can be obtained.
[0014]
The method for manufacturing an active matrix substrate according to the present invention includes a step of forming a scanning line on the substrate, and a step of forming a signal line intersecting the scanning line on the substrate while being electrically insulated from the scanning line. Forming a switching element near the intersection of the scanning line and the signal line, forming an organic insulating layer covering the scanning line, the signal line, and the switching element on the substrate; Forming a contact hole that penetrates the organic insulating layer in a thickness direction and communicates with the switching element;And aboveOrganic insulation layerPredeterminedRemove areas in the thickness direction by dry etchingAnd forming an alignment film directly on the substrate including the step of exposing the underlying portion of the organic insulating layer and the surface of the organic insulating layer exposing the underlying portion.And a process.
[0015]
According to the present manufacturing method, the organic insulating layer interposed between the pixel electrodes is partly removed in the film thickness direction from the surface layer side by dry etching. A region having a high surface resistance is formed with the portion exposed. In addition, due to such a region having a high surface resistance, adjacent pixel electrodes are in a well-insulated state with respect to surface conduction, and current leakage between pixel electrodes traveling on the surface of the organic insulating layer is prevented.
[0016]
At this time, it is preferable to use a reactive gas containing at least one of fluorine (F), oxygen (O), and chlorine (Cl) for the dry etching. Thereby, the altered layer in the surface layer can be completely removed without damaging the organic insulating layer.
The dry etching may be performed using the pixel electrode as a mask. As a result, a mask for dry etching can be eliminated, and the manufacturing process can be simplified.
In addition, a resist stacked on the pixel electrode when the pixel electrode is patterned may be used as a mask for the dry etching. As a result, damage to the pixel electrode due to dry etching can be suppressed.The
[0018]
Further, a step of cleaning the contact hole by plasma cleaning may be further provided between the step of forming the contact hole and the step of forming the pixel electrode.
According to this manufacturing method, it is possible to remove residues, natural oxide films, and the like attached on the switching element in the step of forming the contact hole by such plasma cleaning, and the pixel electrode and the switching element to be formed thereafter The contact resistance can be reduced. Note that an altered layer having a low resistance is formed in the surface layer portion of the organic insulating layer by plasma cleaning. Of these altered layers, the altered layer located in a region where the pixel electrode is not formed is performed thereafter. A region having a high surface resistance is formed by removing the base portion of the organic insulating layer between the pixel electrodes. For this reason, there is no possibility of leakage current between the pixel electrodes that travels on the surface layer portion of the organic insulating layer. Further, since the dry etching is performed after the pixel electrode is formed, the inside of the contact hole cleaned by the plasma cleaning is not contaminated again by such dry etching.
Furthermore, onThe etching amount of the dry etching is preferably 5 nm to 20 nm. This is because the underlying portion of the organic insulating layer having a high surface resistance is reliably exposed. In the manufacturing method of the active matrix substrate, the plasma cleaning for removing the natural oxide film on the source electrode may cause a deteriorated layer in the upper part of the insulating layer provided between the electrodes, which may cause current leakage. To do. By performing dry etching in the above range, this altered layer can be removed, and the current leakage can be suppressed.
[0019]
DETAILED DESCRIPTION OF THE INVENTION
[First Embodiment]
[Active matrix substrate and display device using the same]
1 and 2 are a cross-sectional view and a plan view, respectively, for explaining the configuration of a liquid crystal display device which is an example of the display device of the present invention. 1 (a) and 3 (a) to 7 (a) are cross-sectional views taken along the line Ia-Ia 'of FIG. 2, respectively, and FIGS. 1 (b), 3 (b) to 7 (b). Shows cross-sectional views taken along line Ib-Ib 'of FIG. In addition, the film thicknesses and dimensional ratios of the components are appropriately changed.
[0020]
As shown in FIGS. 1 and 2, the liquid crystal display device of this embodiment includes an active matrix substrate 50, a counter substrate 60, and a liquid crystal layer 70 as a light modulation layer held between the substrates 50 and 60. It is prepared for.
The active matrix substrate 50 is formed on the substrate body 1 made of glass, plastic, or the like by electrically insulating a plurality of scanning lines 15 and signal lines 12 in the row direction and the column direction, respectively. In the vicinity of the intersection of the signal lines 12, a TFT 30 having a gate electrode 2, a drain electrode 6, and a source electrode 7 is formed as a switching element. In the following, on the substrate 1, a region where the pixel electrode 10 is formed, a region where the switching element 30 is formed, a region where the scanning line 15 and the signal line 12 are formed are a pixel region 101, a device region 102, and a wiring, respectively. This is called area 103.
[0021]
The TFT 30 of this embodiment has an inverted staggered structure, and a gate electrode 2, a gate insulating film 3, a semiconductor layer 4, 5, a drain electrode 6 and a source electrode 7 are formed in this order from the bottom layer of the substrate 1 serving as a main body. Has been. That is, a part of the scanning line 15 is extended to form the gate electrode 2, and the island-like semiconductor layer 4 is formed on the gate insulating layer 3 covering the gate line 2 so as to straddle the gate electrode 2 in plan view. A drain electrode 6 is formed on one end of the semiconductor layer 4 via the semiconductor layer 5, and a source electrode 7 is formed on the other end via the semiconductor layer 5.
As the substrate 1, a transparent insulating substrate such as synthetic resin such as polyvinyl chloride, polyester, polyethylene terephthalate, or natural resin can be used in addition to glass.
The gate electrode 2 includes one or more metals such as aluminum (Al), molybdenum (Mo), tungsten (W), tantalum (Ta), titanium (Ti), copper (Cu), chromium (Cr). It is made of an alloy such as Mo-W and is formed integrally with the scanning lines 15 arranged in the row direction as shown in FIG.
[0022]
The gate insulating layer 3 is made of silicon oxide (SiO_x) Or silicon nitride (SiN)_y) And the like, and is formed on the entire surface of the substrate 1 so as to cover the scanning line 15 and the gate electrode 2.
The semiconductor layer 4 is an i-type semiconductor layer made of amorphous silicon (a-Si) or the like that is not doped with impurities, and a region facing the gate electrode 2 through the gate insulating layer 3 is configured as a channel region. .
[0023]
The drain electrode 6 and the source electrode 7 are made of a metal such as Al, Mo, W, Ta, Ti, Cu, and Cr and an alloy containing one or more of these metals, and sandwich the channel region on the i-type semiconductor layer 4. So as to face each other. The drain electrode 6 is formed integrally with the signal line 12 arranged in the column direction. In order to obtain good ohmic contact between the i-type semiconductor layer 4 and the drain electrode 6 and the source electrode 7, phosphorus (P) or the like is provided between the i-type semiconductor layer 4 and the electrodes 6 and 7. An n-type semiconductor layer 5 doped with a high V group element is provided.
[0024]
Insulating layers 8 and 9 are laminated on the substrate 1, and a pixel electrode 10 is formed on the insulating layer 9.
A plurality of pixel electrodes 10 are formed in a matrix on the organic insulating layer 9, and one pixel electrode 10 is provided corresponding to a region partitioned by the scanning lines 15 and the signal lines 12. The pixel electrode 10 has a scanning line 15 and a signal whose end sides are arranged in the lower layers of the insulating layers 8 and 9 except for the corner region (element region 102) where the TFT 30 is formed in the region. It is arranged along the line 12, and substantially all the region of the substrate 1 excluding the TFT 30, the scanning line 15, and the signal line 12 is set as the pixel region 101.
For these pixel electrodes 10, a light-transmitting conductive film such as tin-doped indium oxide (ITO) or zinc-doped indium oxide (IZO) can be used. In the case of using for a reflective display device, a conductive film having high light reflectivity such as aluminum (Al) may be used.
[0025]
The insulating layer formed on the substrate 1 is made of silicon nitride (SiN_y) And the like, and an organic insulating layer 9 made of acrylic resin, polyimide resin, benzocyclobutene polymer (BCB), etc. It comes to strengthen the function. The organic insulating layer 9 has 1 × 10¹³A member having a high surface resistance of Ω or higher is used to prevent a leak current between the pixel electrodes 10. Further, the organic insulating layer 9 is laminated on the substrate 1 relatively thickly to ensure insulation between the pixel electrode 10 and the TFT 30 and the wirings 15 and 12, and a large parasitic capacitance is generated between the pixel electrode 10 and the pixel electrode 10. In addition to preventing, the step structure of the substrate 1 formed by the TFT 30 and the wirings 15 and 12 is flattened by the thick organic insulating layer 9. Note that a photosensitive acrylic resin is preferably used for the organic insulating layer 9, thereby simplifying the process for forming the contact hole, as will be described later in the section “Manufacturing Method of Active Matrix Substrate”. Can be
[0026]
Further, a contact hole 16 penetrating the insulating layers 8 and 9 in the film thickness direction is formed above the source electrode 7, and the insulating layer 9 is formed on the insulating layer 9 through the conductive portion 10 a formed in the contact hole 16. The pixel electrode 10 formed on the source electrode 7 and the source electrode 7 disposed below the insulating layer 8 are electrically connected.
Further, in the non-pixel regions of the organic insulating layer 9 such as the element region 102 and the wiring region 103, a recess G formed by removing a part of the surface layer portion is provided, and a base portion of the organic insulating layer 9 is exposed. It has become. The surface of the recess G is the same as the base portion of the organic insulating layer 9 1 × 10¹³In order to exhibit a high surface resistance of Ω, the adjacent pixel electrodes 10 are in a well-insulated state with respect to surface conduction.
[0027]
An alignment film 51 made of polyimide or the like that has been subjected to a predetermined alignment process such as rubbing is further formed on the substrate 1 thus configured to cover the pixel electrode 10 and the organic insulating layer 9. .
On the other hand, the counter substrate 60 is formed with a transparent counter electrode (common electrode) 62 such as ITO or IZO on a translucent substrate body 61 made of glass, plastic, or the like so as to correspond to at least the display area. Further, an alignment film 63 made of polyimide or the like subjected to a predetermined alignment process is formed at a position corresponding to at least the display region of the substrate 61.
The substrates 50 and 60 configured as described above are bonded to each other by a thermosetting sealing material (not shown) applied to the periphery of the substrate in a rectangular frame shape, and are disposed between the substrates 50 and 60. The liquid crystal 70 is sealed in a space sealed by a substrate (50, 60) and a sealing material while being held at a constant distance by a member (not shown).
[0028]
Therefore, according to the active matrix substrate of the present embodiment, the concave portion in which the underlying portion of the organic insulating layer 9 having a high surface resistance is exposed in the element region 102 and the wiring region 103 where the pixel electrode is not formed on the surface of the organic insulating layer 9. Therefore, the pixel electrodes 10 adjacent to each other in such a high resistance region are in a well-insulated state with respect to surface conduction, and current leakage between the pixel electrodes 10 is prevented.
Further, a high-quality display can be obtained by configuring a display device using an active matrix substrate in which such current leakage between the pixel electrodes 10 is prevented. In particular, when such an active matrix substrate 50 is used in a transmissive liquid crystal display device, the surface resistance of the recess G is 1 × 10.¹³Since it is Ω, the display contrast can be 300 or more (see FIG. 12).
Note that the uppermost layer portion of the organic insulating layer 9 formed under the pixel electrode 10 is an altered layer 14 whose resistance has been reduced by a plasma treatment applied in an active matrix substrate manufacturing method described later. .
[0029]
[Manufacturing method of active matrix substrate]
Next, as an example of a method for manufacturing the active matrix substrate 50 of the present invention, a method for manufacturing a TFT array substrate will be described with reference to FIGS.
[0030]
First, a TFT 30, a scanning line 15, and a signal line 12 as shown in FIGS. 3A and 3B are formed on a substrate 1 such as glass or plastic by a known method. As a method for manufacturing such a TFT 30, for example, first, a metal such as Al, Mo, W, Ta, Ti, Cu, Cr, or an alloy containing these is formed on the substrate 1 by sputtering, and a photolithography process is performed. Then, the gate electrode 2 and the scanning line 15 are patterned by an etching process. Next, on top of this, by means of plasma CVD, sputtering, etc._xAnd SiN_yA gate insulating layer 3 made of a silicon-based insulating film is formed. Then, the i-type semiconductor layer 4 and the n-type semiconductor layer 5 made of a-Si or the like are formed without being exposed to the air, and the semiconductor layers 4 and 5 are patterned in an island shape by a photolithography process and an etching process. Next, a metal such as Al, Mo, W, Ta, Ti, Cu, Cr, or an alloy containing these is formed thereon by sputtering, and the drain electrode 6, the source electrode 7, and the signal line 12 are formed by etching. Form a pattern. Next, the n-type semiconductor layer 5 is etched and separated using the drain electrode 6 and the source electrode 7 as a mask.
[0031]
Next, silicon nitride (SiN) is formed on the substrate 1 by plasma CVD so as to cover the TFT 30, the scanning line 15, and the signal line 12._x), And an organic insulating layer 9 made of acrylic resin, polyimide resin, BCB or the like is applied by spin coating to form a stepped structure by the TFT 30 and the wirings 15 and 12. Flatten as much as possible. Then, a through hole is formed in the organic insulating layer 9 above the source electrode 7. At this time, when a photosensitive resin is used as the organic insulating layer 9, a through-hole is formed in the organic insulating layer 9 by exposing and developing the organic insulating layer 8, so that the manufacturing process can be simplified. . Further, when a non-photosensitive resin is used, a through hole is formed by dry etching or the like.
Next, with the organic insulating layer 9 as a mask, SF₆, O₂, Ar is used to dry-etch with a reactive gas to remove the inorganic insulating layer 8 on the bottom surface of the through hole, thereby forming a contact hole 16 leading from the surface of the organic insulating layer 9 to the source electrode 7 (FIG. 4A, FIG. 4 (b)).
[0032]
At this time, since the exposed surface of the source electrode 7 is contaminated by etching residues, the natural oxide film 13 and the like, a surface treatment for cleaning the contact hole 16 is required. Specifically, using the insulating layers 8 and 9 as a mask, plasma cleaning (reverse sputtering) using Ar gas is performed to remove contaminants such as etching residues on the source electrode 7 and the natural oxide film 13 (FIG. 5). (A) See FIG. 5B). Note that the surface of the organic insulating layer 9 is partially carbonized by this plasma cleaning, and the altered layer 14 having a low resistance is formed.
[0033]
Next, a conductive film is formed on the insulating layers 8 and 9 including the inner surface of the contact hole 16 by sputtering, and a plurality of pixel electrodes 10 are patterned in a matrix shape by etching (FIGS. 6A and 6). (See (b)). When an active matrix substrate is used for a transmissive display device, a conductive film having high light transmittance such as ITO or IZO is formed as such a conductive film, and when used for a reflective display device, Al is used. A conductive film having high light reflectivity such as a film is formed.
Next, in order to restore the insulating property of the surface of the organic insulating layer 9 where the pixel electrode 10 is not formed, a surface treatment for modifying or removing the surface layer portion of the organic insulating layer 9 is performed. This is because current leakage may occur between the adjacent pixel electrodes 10 due to the low resistance altered layer 14 formed on the surface of the organic insulating layer 9 in the plasma cleaning step.
[0034]
Specifically, a part of the surface layer portion of the organic insulating layer 9 is removed by dry etching using the pixel electrode 10 as a mask, and the region where the pixel electrode 10 is not formed on the surface of the organic insulating layer 9 (that is, the element region 102 and In the wiring region 103), a region (concave portion G) where the base portion of the organic insulating layer 9 having a high surface resistance is exposed is formed (see FIGS. 7A and 7B). Thus, according to the method of removing the deteriorated layer, it is not necessary to maintain consistency with other processes, and the degree of freedom of the process is not impaired as in the conventional case. Further, when dry etching is performed using the pixel electrode 10 itself as a mask, it is not necessary to newly provide a mask for etching, and the manufacturing process can be simplified. At this time, in order not to damage the pixel electrode 10, O 2 is used as a reactive gas.₂, SF₆, CF₄, Cl₂, HCl, BCl₃Etc., using a reaction gas containing at least one of fluorine (F), oxygen (O), and chlorine (Cl). Since such a reactive gas has a small etching rate of ITO or the like, by using such a gas, it is possible to etch only the organic insulating layer 9 while suppressing damage to the pixel electrode 10 as much as possible.
[0035]
Further, after forming a protective film on the pixel electrode 10, the dry etching may be performed using the protective film as a mask. Thereby, damage to the pixel electrode 10 can be reliably prevented. As the protective film, a resist stacked on the pixel electrode 10 when the pixel electrode 10 is patterned can be used. By reusing such a resist without peeling after the pixel electrode 10 is formed, there is no need to newly form a protective film, and the manufacturing process can be simplified. In particular, metals such as Al and Cr are Cl.₂, HCl, BCl₃Therefore, when dry etching is performed using a reactive gas containing Cl, it is desirable to mask the pixel electrode 10 with a protective film such as a resist. Although depending on the conditions of plasma cleaning, since the layer thickness of the altered layer 14 is approximately 5 nm, the amount of dry etching is preferably about 5 nm to 20 nm. Thereby, the base portion of the organic insulating layer 9 having a high surface resistance is reliably exposed.
Finally, an alignment film 51 made of polyimide or the like is formed on the entire surface of the substrate 1 by printing or spin coating, and a predetermined alignment process such as rubbing is performed (see FIG. 1).
As described above, the TFT array substrate 50 is manufactured.
[0036]
Therefore, according to the manufacturing method of the active matrix substrate described above, the surface layer portion of the organic insulating layer 9 in the region where the pixel electrode 10 such as the element region 102 and the wiring region 103 is not formed is removed by dry etching. A recess G having a high surface resistance is formed between the adjacent pixel electrodes 10 and the underlying portion of the organic insulating layer 9 is exposed. Thereby, adjacent pixel electrodes 10 are in a well-insulated state with respect to surface conduction, and current leakage between the pixel electrodes 10 is prevented.
At this time, since dry etching is performed using a reaction gas containing at least one of fluorine (F), oxygen (O), and chlorine (Cl), organic insulation is performed while suppressing damage to the pixel electrode 10 as much as possible. Layer 9 can be etched.
[0037]
As described above, in the active matrix substrate of this embodiment, an insulating substrate is used as the substrate 1 as a main body. However, in addition to this, an insulating film is formed on a conductive substrate such as stainless steel. The TFT 30 and various wirings 15 and 12 may be formed on the insulating film.
The insulating layer that insulates the TFT 30 and the wirings 15 and 12 from the pixel electrode 10 is not limited to the two-layer structure including the inorganic insulating layer 8 and the organic insulating layer 9 as described above, but only the organic insulating layer 9. But you can.
Furthermore, the organic insulating layer 9 has a bulk resistance of 1 × 10¹³Instead of Ω or more, only the resistance of the surface layer portion where the concave portion G is formed by a predetermined surface treatment is 1 × 10¹³You may make it become more than (omega).
In addition to the liquid crystal, the light modulation layer 70 may be a dispersion medium in which colored charged particles are dispersed, whereby the display device can be an electrophoretic display device. Further, the display device may be any of a transmissive type, a reflective type, and a transflective type.
[0038]
[Second Embodiment]
[Active matrix substrate and display device using the same]
FIG. 8 is a cross-sectional view for explaining the configuration of the active matrix substrate according to the present invention. 8A to 11A show cross-sectional views taken along the line Ia-Ia ′ of FIG. 2, and FIGS. 8B to 11B show cross-sectional views taken along the line Ib-Ib ′ of FIG. ing. In addition, the film thicknesses and dimensional ratios of the components are appropriately changed. Further, the same components as those in the first embodiment are denoted by the same reference numerals, a description thereof is partially omitted, and FIG.
[0039]
As shown in FIG. 8, the display device according to the present embodiment is provided between an active matrix substrate 50 ′ and a counter substrate 60 arranged opposite to the active matrix substrate 50 ′, as in the first embodiment shown in FIG. The liquid crystal layer 70 as a light modulation layer is held.
As in the first embodiment, the active matrix substrate 50 'includes a plurality of scanning lines 15 arranged in the row direction and a plurality of signal lines 12 arranged in the column direction on the substrate body 1, A TFT 30 as a switching element is provided in the vicinity of the intersection between the scanning line 15 and the signal line 12. On the substrate 1, an insulating layer having a two-layer structure including an inorganic insulating layer 8 and an organic insulating layer 9 is laminated, and a pixel electrode 10 is formed on the organic insulating layer 9.
In the active matrix substrate 50 ′ of the present embodiment, the organic insulating layer 9 between the pixel electrodes 10 is completely removed in the film thickness direction instead of forming the recess G in the organic insulating layer 9 between the pixel electrodes 10. Only the points differ from those of the first embodiment. Other configurations of the active matrix substrate 50 ′ and the configuration of the display device using the same are the same as those in the first embodiment, and thus description thereof is omitted.
[0040]
That is, the organic insulating layer 9 is formed in an island shape in a region excluding the wiring region 103 (that is, a region including the pixel region 101 and the element region 102), and the organic insulating layer 9 in other regions is completely removed. It has a structure. Therefore, a plurality of organic insulating layers 9 are arranged in a rectangular pattern partitioned by the scanning lines 15 and the signal lines 12 without being connected to each other, and are separated from each other through the alignment film 51. It becomes. Then, one pixel electrode 10 is formed on each organic insulating layer 9 formed in a grid pattern, and is electrically connected to the source electrode 7 disposed below the inorganic insulating layer 8 through the contact hole 16. It is connected.
[0041]
Therefore, according to the active matrix substrate of the present embodiment, the pixel electrodes 10 arranged adjacent to each other can be substantially completely insulated with respect to surface conduction. Thereby, current leakage between the pixel electrodes 10 via the organic insulating layer 9 can be completely prevented.
As described above, in the active matrix substrate of this embodiment, the formation region of the organic insulating layer 9 formed in the island shape is the pixel region 101 and the element region 102, but the adjacent organic insulating layers 9 are mutually connected. Of course, the formation region may partially overlap the wiring region 103 in an isolated state.
[0042]
[Manufacturing method of active matrix substrate]
Since the manufacturing method of the active matrix substrate of the present embodiment is the same as the manufacturing method of the active matrix substrate of the first embodiment up to the manufacturing process of the TFT 30, only the processes performed thereafter are shown in FIGS. This will be described with reference to FIG.
[0043]
In this manufacturing method, the inorganic insulating layer 8 made of silicon nitride (SiNx) is formed by plasma CVD on the substrate 1 shown in FIG. 3 on which the TFT 30, the scanning line 15, and the signal line 12 are formed.
Next, an organic insulating layer 9 made of acrylic resin, polyimide resin, BCB or the like is applied by spin coating, and the stepped structure by the TFT 30 and the wirings 15 and 12 is made as flat as possible. Then, a through hole is formed in the organic insulating layer 9 above the source electrode 7 and the organic insulating layer 9 in the wiring region 103 (that is, the region excluding the pixel region 101 and the element region 102) is removed. As a result, rectangular organic insulating layers 9 are formed one by one in each region partitioned by the scanning lines 15 and the signal lines 12 without being connected to each other, and thus formed on the substrate 1. A plurality of organic insulating layers 9 are arranged in a grid pattern.
[0044]
Then, using the organic insulating layer 9 as a mask, SF₆, O₂, Ar is used for dry etching with a reactive gas to remove the inorganic insulating layer 8 on the bottom surface of the through hole formed above the source electrode to form a contact hole 16 (see FIGS. 9A and 9B). ).
Next, using the insulating layers 8 and 9 as a mask, the inside of the contact hole 16 is cleaned by plasma cleaning (reverse sputtering) using Ar gas, and contaminants such as etching residues on the source electrode 7 and the natural oxide film 13 are removed. (See FIG. 10 (a) and FIG. 10 (b)).
[0045]
Next, a conductive film is formed on the insulating layers 8 and 9 including the inner surface of the contact hole 16 by sputtering, and one pixel is formed on each organic insulating layer 9 formed in a grid pattern by etching. The electrode 10 is patterned (see FIGS. 11A and 11B). The altered layer 14 is formed on the organic insulating layer 9 due to plasma damage. However, since the individual organic insulating layers 9 are isolated from each other, the altered layer 14 is formed of the pixel electrode 10. It does not contribute to surface conduction.
Finally, an alignment film 51 made of polyimide or the like is formed on the entire surface of the substrate 1 by printing or spin coating, and a predetermined alignment process such as rubbing is performed (see FIG. 1).
The active matrix substrate 10 is manufactured as described above.
Therefore, according to the manufacturing method of the active matrix substrate, the adjacent organic insulating layers 9 can be isolated from each other by completely removing the organic insulating layers 9 between the pixel electrodes 10 in the film thickness direction. . Thereby, each pixel electrode 10 formed on each organic insulating layer 9 can be completely insulated regarding surface conduction.
[0046]
In addition, this invention is not limited to the above-mentioned embodiment, It can implement in various deformation | transformation in the range which does not deviate from the meaning of this invention.
For example, the TFT 30 is not limited to an inverted staggered structure, and may be a staggered TFT. The switching element is not limited to a TFT, and may be a diode having an MIM (Metal Insulator Metal) structure in which an insulating layer is sandwiched between metal layers.
[0047]
Furthermore, the shape of the pixel electrode 10 is not limited to the shape shown in FIG. 2. For example, when the active matrix substrate is used in a reflective display device, the formation region of the pixel electrode 10 is used as the element region 102 and the wiring. The area 103 can be extended to a rectangular shape partitioned by the scanning lines 15 and the signal lines 12. That is, in the reflective display device, the display is not affected by the structure on the back surface side of the pixel electrode 10, so that the element region 102 and the pixel region 101 are completely overlapped, and the pixel region 101 is connected to the wiring region. By partially overlapping the pixel area 103 and making the pixel region 101 as large as possible, it is possible to increase the aperture ratio and maximize the reflection luminance.
[0048]
【Example】
In order to demonstrate the effect of the present invention, the inventors actually manufactured an active matrix substrate by the manufacturing method according to the present invention. The results will be described below.
The active matrix substrate of the present example is based on the configuration of the first embodiment, and has an organic insulating layer of 10¹³A photosensitive acrylic resin having a surface resistance of Ω was used, and an Al reflector was used as the pixel electrode.
Further, in this embodiment, a good contact resistance between the pixel electrode and the source electrode (10^-2The power for plasma cleaning was set to about 200 W so as to obtain about Ωcm. As a result, the surface layer of the organic insulating layer is altered and the surface resistance is 10⁹Ω-10¹¹Reduced to Ω.
[0049]
Next, the pixel electrode is used as a mask, and Ar gas is 300 sccm and SF is used as a reaction gas.₆Plasma treatment (dry etching) was performed using a mixed gas of 3 sccm of gas, a pressure of 50 mtorr, and a power of 50 W. As a result, the etching rate selection ratio between Al and acrylic resin is 1: 100 or more, and only the acrylic resin can be removed with almost no damage to Al, and the underlying portion of the organic insulating layer with high surface resistance is exposed. I was able to.
[0050]
【The invention's effect】
As described above, according to the present invention, the pixel electrode adjacent to the high-resistance region is formed by providing the concave portion exposing the base portion of the organic insulating layer having a high surface resistance around the pixel electrode. They can be well insulated with respect to surface conduction. Thereby, current leakage between the pixel electrodes via the organic insulating layer can be prevented. Further, by using such an active matrix substrate for a display device, high-quality display can be obtained.
[Brief description of the drawings]
FIGS. 1A and 1B are cross-sectional views illustrating a schematic configuration of a display device according to a first embodiment of the present invention, wherein FIGS. 1A and 1B are a cross-sectional view taken along lines Ia-Ia ′ and Ib-Ib ′ in FIG. FIG.
FIG. 2 is a top view showing a schematic configuration of a display device according to the present invention.
FIGS. 3A and 3B are process diagrams showing a method for manufacturing an active matrix substrate according to the first embodiment of the present invention, wherein FIGS. 3A and 3B are cross-sectional views taken along lines Ia-Ia ′ and Ib-Ib ′ of FIG. FIG.
FIGS. 4A and 4B are process diagrams showing a method of manufacturing an active matrix substrate according to the first embodiment of the present invention, wherein FIGS. FIG.
FIGS. 5A and 5B are process diagrams showing a method for manufacturing an active matrix substrate according to the first embodiment of the present invention, wherein FIGS. 5A and 5B are cross-sectional views taken along lines Ia-Ia ′ and Ib-Ib ′ of FIG. FIG.
FIGS. 6A and 6B are process diagrams illustrating a method of manufacturing an active matrix substrate according to the first embodiment of the present invention, wherein FIGS. 6A and 6B are cross-sectional views taken along lines Ia-Ia ′ and Ib-Ib ′ of FIG. FIG.
FIGS. 7A and 7B are process diagrams showing a method for manufacturing an active matrix substrate according to the first embodiment of the present invention, wherein FIGS. 7A and 7B are cross-sectional views taken along lines Ia-Ia ′ and Ib-Ib ′ of FIG. FIG.
FIGS. 8A and 8B are cross-sectional views showing a schematic configuration of a display device according to a second embodiment of the present invention, wherein FIGS. 8A and 8B show the Ia-Ia ′ cross section and the Ib-Ib ′ cross section of FIG. FIG.
FIGS. 9A and 9B are process diagrams showing a method for manufacturing an active matrix substrate according to a second embodiment of the present invention, wherein FIGS. 9A and 9B are cross-sectional views taken along lines Ia-Ia ′ and Ib-Ib ′ of FIG. FIG.
FIGS. 10A and 10B are process diagrams illustrating a method of manufacturing an active matrix substrate according to a second embodiment of the present invention, wherein FIGS. 10A and 10B are cross-sectional views taken along lines Ia-Ia ′ and Ib-Ib ′ of FIG. FIG.
FIGS. 11A and 11B are process diagrams illustrating a method for manufacturing an active matrix substrate according to a second embodiment of the present invention, wherein FIGS. 11A and 11B are cross-sectional views taken along lines Ia-Ia ′ and Ib-Ib ′ of FIG. FIG.
FIG. 12 is a diagram illustrating a relationship between a leakage current between pixel electrodes and contrast in a transmissive liquid crystal display device.
FIG. 13 is a diagram showing the influence of plasma cleaning on the electrical characteristics of the substrate, and FIG. 13A is a diagram showing the relationship between the plasma cleaning power and the surface resistance of the organic insulating layer surface on which the pixel electrodes are formed. (B) is a figure which shows the relationship between the electric power of plasma cleaning, and the contact resistance between a pixel electrode / source electrode.
[Explanation of symbols]
1 Substrate
6 Drain electrode
7 Source electrode
9 Organic insulation layer
10 Pixel electrode
12 signal lines
15 scan lines
16 Contact hole
30 TFT (switching element)
50 TFT array substrate (active matrix substrate)
60 Counter substrate
62 Counter electrode
70 Liquid crystal layer (light modulation layer)
101 pixel area
102 Element area
103 Wiring area
G recess(Exposed portion of the organic insulating layer underlayer)

Claims (9)

  A substrate, a scanning line provided on the substrate, a signal line provided on the substrate so as to intersect the scanning line, and a switching provided near the intersection of the scanning line and the signal line An element, an organic insulating layer formed on the substrate so as to cover the scanning line, the signal line, and the switching element, and having a contact hole that communicates with the switching element; and the contact formed on the organic insulating layer. A pixel electrode electrically connected to the switching element through a hole, and removing the surface layer portion of the organic insulating layer in a region where the pixel electrode is not formed at least in the organic insulating layer An active matrix substrate, wherein an alignment film is formed directly on an exposed base portion of an insulating layer. 2. The active matrix substrate according to claim 1, wherein the surface resistance of the exposed portion of the organic insulating layer is 1 × 10 ¹³ Ω or more.   An active matrix substrate according to claim 1, a counter substrate having a counter electrode provided to face a pixel electrode of the active matrix substrate, and the active matrix substrate and the counter substrate. A display device comprising: a light modulation layer held therebetween.   Forming a scanning line on the substrate; forming a signal line intersecting the scanning line on the substrate by electrically insulating the scanning line; and near an intersection of the scanning line and the signal line Forming a switching element on the substrate, forming an organic insulating layer covering the scanning line, the signal line, and the switching element on the substrate; penetrating the organic insulating layer in a thickness direction; Forming a contact hole leading to the element; removing a predetermined region of the organic insulating layer in a thickness direction by dry etching to expose a base portion of the organic insulating layer; and a base portion of the organic insulating layer And a step of directly forming an alignment film on the substrate including the exposed surface of the active matrix substrate.   5. The method of manufacturing an active matrix substrate according to claim 4, wherein the dry etching uses a reactive gas containing at least one of fluorine (F), oxygen (O), and chlorine (Cl).   6. The method of manufacturing an active matrix substrate according to claim 4, wherein the dry etching is performed using the pixel electrode as a mask.   6. The method of manufacturing an active matrix substrate according to claim 4, wherein the dry etching is performed by using a resist laminated on the pixel electrode as a mask when the pixel electrode is patterned. .   8. The method according to claim 4, further comprising a step of cleaning the contact hole by plasma cleaning between the step of forming the contact hole and the step of forming the pixel electrode. The manufacturing method of the active matrix substrate as described.   The method for manufacturing an active matrix substrate according to any one of claims 4 to 8, wherein an etching amount of the dry etching is 5 nm to 20 nm.

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