JP4472216B2 - Method for manufacturing active matrix substrate - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a structure of an active matrix substrate for detecting a silicon residue of a thin film transistor and a manufacturing method thereof.
[0002]
[Prior art]
In the manufacture of an active matrix substrate, the silicon residue of amorphous silicon constituting the thin film transistor is a cause of point defects in the liquid crystal panel. Therefore, it is required to reduce the silicon residue in the production of the active matrix substrate in order to improve the yield, but at the same time, the cause of point defects is detected at an early stage of the production process, that is, at a stage of low added value, and the production loss. It is also required to reduce the size. A point defect refers to a phenomenon in which when a liquid crystal panel is irradiated with light, the retention capacity in units of pixels changes, and a luminance difference occurs between a leaking pixel and a normal pixel.
[0003]
In the point defect detection process, a voltage is applied to the thin film transistor (TFT) array on the active matrix substrate to accumulate charges in the auxiliary capacitors of the pixels and held for a certain period of time. Pixels that cannot be held are detected as point defects.
[0004]
As an example, let us consider a case where the silicon residue is generated across one pixel and between adjacent drain wirings in the pixel as shown in FIG. A gate wiring 102 and a gate electrode 112 are formed on a glass substrate 101, covered with a gate insulating film 103, on which an amorphous silicon region (a-Si region 104) of a TFT, a source electrode 116 made of light-shielding Cr, A drain electrode 126 is formed. Here, the pixel electrode 127 formed of a transparent metal is formed in a region where the source electrode 116 is surrounded by the gate wiring 102 and the drain wiring 136. The passivation film 108 formed on the source electrode 116 is partially removed on the source electrode 116 to form a contact through hole 109, and the source electrode 116 and the pixel electrode 127 are connected through the contact through hole 109 portion. The
[0005]
In the above configuration, it is assumed that the silicon residue 124 is generated between the drain wirings 136 when the a-Si region 104 is formed.
[0006]
[Problems to be solved by the invention]
In this case, since the silicon remaining 124 has a high resistance value of 10 ¹² to 10 ¹³ Ω when no light is irradiated, it is difficult to detect a short circuit between the drain wirings 136 due to the silicon remaining. When light irradiation is performed, that is, when display is performed, the resistance becomes as small as 10 ⁵ to 10 ⁶ Ω, but it becomes difficult to discriminate between leakage of the TFT itself and a short circuit between the drain wirings 136, and a defect due to silicon residue is specified. It becomes difficult. Therefore, it is difficult to detect a short circuit due to the silicon residue 124 between adjacent drain wirings, and it is regarded as defective after the display panel is completed, causing an increase in manufacturing loss.
[0007]
Further, among the point defects, the bright point defect means that a part of the display on the display screen is changed. If even one pixel has a bright point defect, the display panel becomes defective. On the other hand, even if a black spot defect that causes black display occurs, a black spot defect of a certain level is allowed because it is complemented by surrounding pixels at the time of display. Therefore, when it is assumed that a silicon residue is generated with a certain probability, how to reliably detect a light spot defect with a small silicon remaining area is a major problem to be solved in terms of manufacturing cost.
[0008]
An object of the present invention is to provide an active matrix substrate in which even if silicon residue is generated during the manufacturing process of the active matrix substrate, the large area silicon residue becomes a black spot defect, and the small area silicon residue can be reliably detected by a detection device, and its manufacture It is to provide a method.
[0009]
[Means for Solving the Problems]
The active matrix substrate of the present invention includes a gate insulating film covering the substrate, a semiconductor region formed on the gate insulating film, source / drain electrodes formed in contact with both ends of the semiconductor region, and the source electrode A protective film covering the drain electrode and formed on the gate insulating film, a contact hole formed on the source / drain electrode by opening a part of the protective film, and covering the contact hole An active matrix substrate comprising a pixel electrode formed on a protective film, wherein the source / drain electrodes are formed in a frame shape under the pixel electrode via the protective film, and simultaneously with the formation of the contact hole An opening that coincides with the inside of the frame-shaped source / drain electrode is formed in the protective film, and the pixel electrode and the front electrode are formed through the contact hole. And source and drain electrodes, characterized in that it is connected.
[0010]
In the active matrix substrate of the present invention, the source / drain electrodes are made of a light shielding metal, the pixel electrodes are made of a transparent metal, or the source / drain electrodes are laminated metal films having a light shielding metal as a lower layer and a transparent metal as an upper layer. The pixel electrode is made of a transparent metal.
[0011]
Furthermore, in the active matrix substrate of the present invention, the frame-shaped source / drain electrodes are formed in a matrix on the gate insulating film, and are formed on the gate insulating film simultaneously with the source / drain electrodes. The drain wiring is wired in one direction between the frame-shaped source / drain electrodes formed in the matrix, and the drain wiring and the frame-shaped portions of the source / drain electrodes located on both sides of the drain wiring A part of the light incident from the side opposite to the side where the source / drain electrodes are formed is shielded.
[0012]
Next, in the method of manufacturing the active matrix substrate of the present invention, the substrate surface is covered with a gate insulating film, a semiconductor region is formed on the gate insulating film, and source / drain electrodes in contact with both ends of the semiconductor region are formed. Forming a protective film on the gate insulating film so as to cover the source / drain electrodes, and forming a contact hole on the source / drain electrodes by opening a part of the protective film. And forming a pixel electrode by depositing and patterning a transparent metal film on the protective film so as to cover the contact hole, and connecting the pixel electrode to the source / drain electrode through the contact hole. In the method of manufacturing a substrate, in the step of forming the source / drain electrodes, the source / drain electrodes are formed. In the region where the pixel electrode is formed, and in the step of forming the contact hole, an opening is formed by opening the protective film on the region where the pixel electrode of the source / drain electrode is formed And a step of performing wet etching over the film thickness of the source / drain electrodes exposed in the opening between the step of forming the contact hole and the step of forming the pixel electrode. .
[0013]
In the method of manufacturing an active matrix substrate according to the present invention, the source / drain electrodes are made of a light shielding metal, and in the wet etching step, a transparent metal film covering the opening is deposited and then exposed to the opening. Wet etching of the source / drain electrode is performed by wet etching the transparent metal film, and further continuing the etching, or the source / drain electrode is formed of a laminated metal film having a light shielding metal as a lower layer and a transparent metal as an upper layer. In the step of forming the contact hole, the source / drain electrode exposed in the opening is removed by wet etching the transparent metal film on the upper layer of the source electrode exposed in the opening, and further continuing the etching. Done.
[0014]
DETAILED DESCRIPTION OF THE INVENTION
An embodiment of the present invention will be described with reference to FIG. FIG. 1A is a plan view of the active matrix substrate side according to the present embodiment, and FIG. 1B is a cross-sectional view taken along a cutting line AA ′ in FIG.
[0015]
The present invention is characterized in a method for manufacturing an active matrix substrate. As a result of the manufacturing method, an active matrix substrate having a structure as shown in FIG. 1 is obtained. The structure of the active matrix substrate has the following characteristics.
[0016]
First, the source electrode 16 and the drain electrode 26 of the TFT are formed by sequentially laminating a light-shielding metal film 6 such as Cr and an ITO film 7 on the a-Si region 4 and patterning them in the same pattern. Here, the source electrode 16 is formed in a frame shape as shown by a cross hatch in a pixel region surrounded by the gate wiring 2 and the drain wiring 36. Therefore, there is no metal inside the frame, and the gate insulating film 3 is exposed. Further, the passivation film 8 formed on the source electrode 16 is partially removed on the source electrode 16 to form a contact through hole 9. The source electrode in the contact through hole 9 portion is formed by the upper ITO film 7. The light shielding metal film 6 is exposed by being removed.
[0017]
Next, a method for manufacturing the active matrix substrate of the present embodiment will be described with reference to FIGS. In these drawings, (a) is a plan view, and (b) is a cross-sectional view taken along a cutting line AA ′ in (a).
[0018]
First, Cr is formed on a transparent insulating substrate 1 such as glass and patterned to form the gate wiring 2 and the gate electrode 12. The gate wiring 2 and the gate electrode 12 are covered with a gate insulating film 3 made of a nitride film (FIG. 2).
[0019]
Next, amorphous silicon is deposited on the gate insulating film 3 and patterned to form the a-Si region 4. Here, for the sake of simplicity, it is assumed that the amorphous silicon region for ohmic contact doped with phosphorus is included as a surface region in the a-Si region 4 (FIG. 3).
[0020]
Next, a light shielding metal film 6 made of Cr or Ti and an ITO film 7 are sequentially formed. A resist pattern for forming electrodes and wirings is formed on the ITO film 7, and the ITO film 7 and the light shielding metal film 6 are sequentially removed by etching using the resist pattern as a mask. As a result, the source electrode 16, the drain electrode 26, and the drain wiring 36 having the light shielding metal film 6 as the lower layer and the ITO film 7 as the upper layer are formed. At this time, the source electrode 16 is formed in substantially the same shape and area as the pixel electrode formed in a later step. A passivation film 8 made of a nitride film is formed to cover these electrodes and wiring (FIG. 4).
[0021]
Next, a part of the passivation film 8 is removed to form a contact hole 9 on the source electrode 16. At this time, the pixel opening 10 is also formed in the central portion of the source electrode 16 corresponding to the pixel electrode. Formed (FIG. 5).
[0022]
Subsequently, the ITO film 7 exposed in the contact hole 9 and the pixel opening 10 is etched. Etching at this time is
Ceric ammonium nitrate (NH ₄ ) ₂ Ce (NO ₃ ) ₆ + Nitric acid HNO ₃
Etching is performed by causing the following reaction.
2Ce ⁴⁺ + Cr → 2Ce ³⁺ + Cr ²⁺
From the above reaction, the ITO film 7 and the underlying Cr are also etched (FIG. 6A). However, if the a-Si region 4 exists under Cr, the positive charge of cerium recombines with the electrons of a-Si and is not supplied to Cr, so that Cr cannot be ionized (dissolved). If a-Si remains under Cr, Cr on a-Si region 4 is not etched.
[0023]
Finally, an ITO film is formed again and patterned to form a pixel electrode 27 connected to the source electrode 16 through the contact hole 9 (FIG. 6B).
[0024]
The cross-sectional view of the TFT shown in FIG. 6B obtained here is the same as the cross-sectional view shown in FIG. 1B, and the plan view is shown in FIG. As shown in FIG. 1A, a source electrode 16 located in a region surrounded by a broken line, a source electrode 46 of an adjacent pixel, and a drain wiring 36 wired between the source electrode 16 and the source electrode 46 are Each includes a light-shielding Cr film and serves to shield light incident from the side of the transparent insulating substrate 1 opposite to the side where the gate electrode 12 is formed. In particular, when a color filter is formed on a counter substrate disposed opposite to the active matrix substrate and a black matrix that shields light between the color filters is formed, the counter substrate may be misaligned with the active matrix substrate. The light leakage of the light from the backlight on the back surface of the active matrix substrate that occurs can be prevented by the above-described source electrode 16, source electrode 46, drain wiring 36, and black matrix.
[0025]
In this embodiment, as shown in FIGS. 5 and 6, the source electrode (and the drain electrode) is a laminated film of a light-shielding metal film and a transparent metal film. However, as shown in FIG. (And the drain electrode) may be configured only by a light-shielding metal film. In this case, the passivation film 8 is deposited on the source electrode 16, and then the opening 10 having the same shape as that of the above embodiment is formed, and the ITO film 7 covering the opening is further deposited (FIG. 7B). As it is, the ITO film 7 is wet-etched with the same etching solution as in the above embodiment (FIG. 7C). Similar to the above embodiment, if a-Si remains under Cr, Cr remains. If a-Si does not exist under Cr, Cr is removed by etching. Subsequently, an ITO film is formed again and patterned to form a pixel electrode 27 connected to the source electrode 16 through the contact hole 9 (FIG. 7D).
[0026]
Next, the effect of the present invention will be described with reference to FIGS. In these drawings, (a) is a plan view, and (b) is a cross-sectional view taken along a cutting line in (a).
[0027]
As shown in FIG. 8, when the silicon residue 24 is generated in an abnormally small area, Cr on the silicon residue 24 remains without being etched, so that the source electrode 16 and the drain wiring 36 are connected by Cr. Therefore, regardless of whether the TFT is on or off, the source electrode 16 always has the same potential as the drain wiring 36, and a pixel defect is easily detected. Further, since the pattern abnormality is a small area, it is possible to cut the remaining silicon 24 and Cr thereon with a laser to obtain a normal pixel.
[0028]
As shown in FIG. 9, when the silicon residue 44 remains in a large area due to the pattern abnormality, the Cr on the silicon residue 44 remains without being etched, so that most of the pixel region is light during display due to the large area of Cr. Is shielded from light and becomes a black spot defect. Therefore, when the silicon remaining 44 remains in a large area, Cr also remains large in the same shape, so that the pixel defect becomes a black spot defect, and if the defect is within a range allowed as a black spot defect, it is not regarded as defective. It can also be used as a product.
[0029]
【The invention's effect】
As described above, in the active matrix substrate and the manufacturing method thereof according to the present invention, a Cr film is formed in advance on the pixel electrode region that occupies a large area as a part of the source / drain electrode at the same time as the formation of the source / drain electrode. In addition, an ITO film is formed so as to be in direct contact with the source / drain electrodes, and etching of the ITO film is performed using ceric ammonium nitrate (NH ₄ ) ₂ Ce (NO ₃ ) ₆ + nitric acid HNO ₃ . And wet etch. At this time, if a-Si remains between the wirings under the Cr film, the Cr film on the a-Si remains due to the battery action of the etching solution. Facilitates detection.
[Brief description of the drawings]
1A and 1B are a plan view and a cross-sectional view showing an embodiment of the present invention.
FIG. 2 is a cross-sectional view showing an embodiment of the present invention in the order of manufacturing steps.
3 is a cross-sectional view showing a manufacturing step that follows FIG. 2; FIG.
4 is a cross-sectional view showing a manufacturing step that follows FIG. 3; FIG.
FIG. 5 is a cross-sectional view showing a manufacturing step that follows FIG. 4;
6 is a cross-sectional view showing a manufacturing step that follows FIG. 5; FIG.
FIG. 7 is a cross-sectional view showing a manufacturing method according to a modification of the embodiment of the present invention in the order of manufacturing steps.
FIG. 8 is a cross-sectional view showing a state of remaining silicon when an embodiment of the present invention is applied.
FIG. 9 is a cross-sectional view showing another state of remaining silicon when the embodiment of the present invention is applied.
FIG. 10 is a cross-sectional view showing a state of silicon remaining in a conventional active matrix substrate.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1,101 Transparent insulating substrate 2,102 Gate wiring 3,103 Gate insulating film 4,104 a-Si area | region 6 Light shielding metal film 7 ITO film 8,108 Passivation film 9,109 Contact hole 10 Opening part 12,112 Gate wiring 16, 46, 116 Source electrodes 24, 44, 124 Remaining silicon 26, 126 Drain electrodes 27, 127 Pixel electrodes 36, 136 Drain wiring

Claims (3)

Covering the substrate surface with a gate insulating film, forming a semiconductor region on the gate insulating film, forming a source / drain electrode in contact with both ends of the semiconductor region, covering the source / drain electrode, and Depositing a protective film on the gate insulating film; opening a part of the protective film to form a contact hole on the source / drain electrode; and covering the contact hole with a transparent metal on the protective film Depositing a film and patterning to form a pixel electrode, and connecting the pixel electrode to the source / drain electrode through the contact hole, wherein the source / drain electrode is formed In the forming step, a Cr film is formed in a region where the pixel electrode is formed, and the contact hole is formed. A step of opening the protective film on a region where the pixel electrode of the source / drain electrode is formed to form an opening, forming the contact hole, and forming the pixel electrode. A method for manufacturing an active matrix substrate, comprising: a step of wet etching the Cr film exposed in the opening with ceric ammonium nitrate + nitric acid over the film thickness. The source / drain electrodes are made of a light shielding metal, and in the wet etching step, after depositing a transparent metal film covering the opening, the wet etching of the source / drain electrode exposed in the opening is performed by the transparent metal. the film is wet-etched, a method of manufacturing the active matrix substrate according to claim 1, wherein performed by further continuing the etching. The source / drain electrodes are made of a laminated metal film having a light shielding metal made of a Cr film as a lower layer and a transparent metal as an upper layer, and in the step of forming the contact hole, the removal of the source / drain electrodes exposed to the opening is the opening. wet etching the upper layer of the transparent metal film of the source electrode exposed to the section, the method of manufacturing the active matrix substrate according to claim 1, wherein performed by further continuing the etching.

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