JP2007206134A - Method of manufacturing active matrix display device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method of manufacturing an active matrix display device like a liquid crystal display device, which uses insulated-gate field effect thin film transistors TFT as switching elements and has less bright points based on short-circuit between source electrodes and drain electrodes of these TFTs. <P>SOLUTION: The method of manufacturing the active matrix display device includes steps of; forming a photo resist layer 30 having a prescribed pattern on a surface of a metallic layer which has at least a surface layer made of molybdenum and has a multi-layered structure, and then etching this metallic layer; removing the photo resist layer 30 on the surface of the metallic layer by ashing; washing with water; and laminating a passivation layer on the surface including the metallic layer. The step of washing with water is continued for such time or longer that stains like water drops will not occur after this step. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

The present invention relates to a method for manufacturing an active matrix display device, and more particularly, based on a short circuit between a source electrode and a drain electrode of an TFT using an insulated gate field effect thin film transistor TFT (Thin Film Transistor) as a switching element. The present invention relates to a method for manufacturing an active matrix display device such as a liquid crystal display device that generates less bright spots.

First, taking an active matrix type liquid crystal display device as an example of the display device, the configuration will be briefly described with reference to FIG. 2 which is a plan view of several pixel portions and FIG. 3 which is a cross-sectional view taken along the line AA of FIG. To do. The liquid crystal display device 10 includes an array substrate AR and a color filter substrate CF. Among these, the array substrate AR is provided for each region surrounded by the scanning lines Xn, Xn + 1... And the signal lines Ym, Ym + 1. A pixel electrode 12 is provided on the substrate. A storage capacitor electrode 14 is provided under the pixel electrode 12 via a gate insulating film 13.
The pixel electrode 12 is connected to the drain electrode D of the driving TFT. Note that an alignment film (not shown) is formed on at least the surface of the pixel electrode 12.

Further, the color filter substrate CF is provided with a common electrode 17 and an alignment film (not shown) via the color filter layer 16 on the surface of the second light transmitting substrate 15. The source electrode S of the TFT is connected to the signal lines Ym, Ym + 1..., And the drain electrode D is connected to the pixel electrode 12 via the contact hole 18. Further, the gate electrode G of the TFT is connected to the scanning lines Xn, Xn + 1... So that a gate pulse having a predetermined voltage is applied. In the liquid crystal display device 10 shown here, each TFT, the scanning line Xn
, Xn + 1... And the signal lines Ym, Ym + 1..., The interlayer film 20 is flattened to a predetermined height through the passivation layer 19 over the entire display area of the first light-transmissive substrate 11. It is provided to become. The pixel electrode 12 is provided on the surface of the interlayer film 20, and a cell gap,
That is, the distance between the pixel electrode 12 and the common electrode 17 is kept constant.
The pixel electrode 12 and the common electrode 17 are usually made of transparent ITO (Indium Tin Oxide) or IZO (Indium Zinc Oxide). A liquid crystal 21 is sealed between the array substrate AR and the color filter substrate CF.

The array substrate AR of the liquid crystal display device 10 is generally manufactured as follows (see Patent Documents 1 to 3 below). First, the glass substrate as the first translucent substrate 11 is washed to clean the surface. Next, a first metal layer made of, for example, a two-layer film of aluminum and molybdenum is formed on the entire surface of the glass substrate by a method such as sputtering. Among these, aluminum is used as a low resistance wiring, and molybdenum is used for securing an ohmic contact with a semiconductor layer, a transparent conductive electrode, and the like and for imparting oxidation resistance to aluminum.

Next, after washing the substrate, a photoresist is applied and dried, exposed through a mask pattern in which a predetermined pattern is formed, and developed to form a photoresist having the mask pattern transferred onto the substrate. After the metal is cured by heating, the first metal layer is wet-etched, and the gate electrode G of the TFT, the scanning lines Xn, Xn + 1.
4 are formed in a predetermined pattern. Thereafter, the photoresist is stripped using a stripping solution.

Next, a gate insulating film made of silicon oxide or silicon nitride, a semiconductor layer made of amorphous silicon (a-Si) or polysilicon (p-Si), and an ohmic contact layer are successively formed on the substrate by plasma CVD. To do. Of these, the ohmic contact layer is a-
An n ⁺ a-Si layer or an n ⁺ p-Si layer in which Si or p-Si is doped with a small amount of phosphorus is used.

Next, a photoresist is applied and dried, exposed through a mask pattern in which a predetermined pattern is formed, and developed to form a photoresist having the mask pattern transferred onto the substrate, and the photoresist is cured by heating. Thereafter, the semiconductor layer and the ohmic contact layer are formed into a predetermined pattern by dry etching using, for example, a mixed gas of SF ₆ and O ₂ or a mixed gas of CF ₄ and O ₂ . Thereafter, the photoresist is stripped using a stripping solution.

Next, after cleaning the substrate, a second metal layer made of, for example, a three-layer film of molybdenum / aluminum / molybdenum is formed over the entire surface of the glass substrate by a method such as sputtering. Next, a photoresist is applied and dried, exposed through a mask pattern in which a predetermined pattern is formed, and developed to form a photoresist having the mask pattern transferred onto the substrate, and the photoresist is cured by heating. Later, the second metal layer is wet-etched to pattern the TFT source electrode S, drain electrode D, signal lines Ym, Ym + 1,... Into a predetermined shape, and the photoresist is stripped using a stripping solution.

Next, a part of the ohmic contact layer exposed to the channel portion 23 is etched by dry etching using, for example, a mixed gas of SF ₆ and O ₂ or a mixed gas of CF ₄ and O ₂ .

Next, the substrate is cleaned, and a passivation layer 19 made of silicon nitride or silicon oxide is formed on the entire substrate by plasma CVD or the like. Further, an interlayer made of photoresist or the like is formed on the surface of the passivation layer 19 over the entire display area. By applying, exposing and developing the film 20, an opening in the contact hole 18 portion of the interlayer film is formed. Next, after applying a photoresist to the entire surface, a photomask pattern designed so that an opening can be formed in the passivation film in the contact hole portion, and exposure and etching are performed to form an opening in the passivation layer 19 having a predetermined pattern. Formed, then ITO or IZ
By forming the pixel electrode 12 made of a transparent conductive material such as O in a predetermined pattern, the pixel electrode 12 and the drain electrode D of the TFT as a switching element are electrically connected in the contact hole 18. Furthermore, an alignment film is formed on the surface of the pixel electrode 12 or the like.
Details thereof are omitted.
JP 10-268353 A (claims, paragraphs [0057] to [0086]) JP 2002-261287 A (paragraphs [0036] to [0053]) JP 2004-177946 A (paragraphs [0026] to [0039])

A conventional liquid crystal display device is manufactured by the above-described manufacturing method, but before forming a passivation film, oxygen or ozone gas is used at a high frequency for the purpose of uniformizing TFT characteristics and cleaning the surface of the gate insulating film. The channel portion 23 of the semiconductor layer 22 is converted into plasma by
In some cases, a dry oxidation treatment step for exposing the substrate is optionally performed. However, after this dry oxidation treatment step, bright spot generation based on a short circuit between the source electrode and the drain electrode was occasionally found. The inventors of the present application have conducted various studies on the cause of the short circuit between the source electrode and the drain electrode. As an example of the cause, for example, B surrounded by a dotted circle in FIG.
As shown in FIG. 4 which is a schematic enlarged view of the portion, the drain electrode D and the signal lines Ym, Ym + 1 ·
There are shorts due to water-drop-like dirt 25 generated between them and short-circuits caused by water-drop-like dirt generated between the channels 23 between the drain electrode D and the source electrode S. It has been found that oxides mainly composed of molybdenum are contained in the soil.

The oxide mainly composed of molybdenum in the water droplets is not molybdenum oxide because it dissolves in the etchant as a water-soluble salt during wet etching, so it does not become molybdenum oxide at the same time during the dry oxidation process. It is presumed that the exposed molybdenum was formed by oxidation. Accordingly, the inventors of the present application have observed the molybdenum oxide formation process from various viewpoints, and as a result, molybdenum oxide that is easily peeled off from the surface of the molybdenum metal since the dry oxidation treatment process was performed on the molybdenum. It is found that it takes time to form the drain electrode D and the signal lines Ym and Ym + 1 caused by the water droplet-like dirt dramatically by reviewing the process up to the water washing process performed after the dry oxidation process. Since the inventors have found that the short-circuit between the drain electrode D and the drain electrode D and the source electrode S between the drain electrode D and the source electrode S can be reduced, and the present invention has been completed. is there.

That is, according to the present invention, a short circuit due to water droplets between the drain electrode and the signal line of the TFT or a short circuit due to water droplets generated between the channels 23 between the drain electrode D and the source electrode S is reduced. An object of the present invention is to provide a method of manufacturing an active matrix display device that can be made to operate.

The above object of the present invention can be achieved by the following configurations. That is, the manufacturing method of the active matrix display device according to claim 1 is:
(1) forming a metal layer having at least a surface layer of molybdenum after forming a semiconductor layer on the surface of the gate insulating film;
(2) forming a channel layer of a thin film transistor, a source electrode, a drain electrode, and a signal line by forming a photoresist layer having a predetermined pattern on the surface of the metal layer and then etching the metal layer;
(3) removing the photoresist;
(4) water washing step,
(5) laminating a passivation layer on the surface including the metal layer;
In an active matrix display device manufacturing method including:
Between the steps (3) and (4), a step of performing a dry oxidation treatment on a part of the channel portion of the thin film transistor and then leaving it for a predetermined time is provided.

It should be noted that providing a step of leaving for a predetermined time after the dry oxidation treatment step is an undesirable matter from the viewpoint of work efficiency, but in the present invention, the step of leaving for a predetermined time which is not preferable in the related art. It is essential to provide

According to a second aspect of the present invention, in the method for manufacturing an active matrix display device according to the first aspect, the step of performing the dry oxidation process is a photo-excited oxidation process or a plasma oxidation process using oxygen or ozone gas. It is characterized by that.

According to a third aspect of the present invention, in the method of manufacturing an active matrix display device according to the first aspect, the passivation layer is made of silicon nitride.

According to a fourth aspect of the present invention, in the method for manufacturing an active matrix display device according to any one of the first to third aspects, the predetermined time is 60 minutes or more.

By providing the above configuration, the present invention has the following excellent effects. That is, when a part of the channel portion of the thin film transistor is subjected to a dry oxidation process, a part of the molybdenum on the surface of the metal layer exposed at the same time is oxidized. It becomes a stable oxide of molybdenum that easily peels off, and is attached to the surface of the molybdenum metal. Therefore, according to the first aspect of the present invention, the molybdenum oxide generated when a part of the channel portion of the thin film transistor is subjected to the dry oxidation treatment is easily peeled off during the water washing step and sufficiently washed away. As a result, no water droplet-like contamination due to the oxide of the oxide is generated, so that a short circuit between adjacent metal layers due to the oxide of molybdenum is eliminated, and defects of the active matrix display device are reduced.

According to the invention of claim 2, in addition to the effect of the invention of claim 1, it is possible to complete a TFT having a uniform characteristic with less surface contamination of the gate insulating film. Thus, an active matrix display device with little quality variation and good display image quality can be obtained.

According to the invention of claim 3, silicon nitride is a well-known material having good characteristics as a passivation layer, but the passivation layer made of this silicon nitride is formed on the surface cleaned through the water washing step. Therefore, the surface of the metal layer and the like can be well protected from the surrounding environment.

According to the invention of claim 4, when the predetermined time is at least 60 minutes,
Even in various types of display devices that are generally manufactured, molybdenum oxide can be sufficiently washed away in a short washing step, and water droplets caused by molybdenum oxide are substantially not generated. Thus, an active matrix display device with few defects due to the molybdenum oxide can be manufactured. A more preferable predetermined time is 90 minutes or more, and most preferably 120 minutes or more.

Hereinafter, a specific example of a method for manufacturing a display device according to the present invention will be described in detail with reference to FIG. However, the following embodiments are described by taking a transmissive liquid crystal display device for embodying the technical idea of the present invention as an example, and are not intended to specify the present invention.
The present invention can be equally applied to various active matrix display devices having TFTs as switching elements. 1 is a cross-sectional view of a portion corresponding to the line AA in FIG. 2 during the manufacturing process of the array substrate of the liquid crystal display device. In FIG. 1, the same reference numerals are given to the same components as those of the conventional liquid crystal display device shown in FIGS.

First, a step of cleaning a glass substrate as the first light-transmitting substrate 11, a step of forming a first metal layer composed of a two-layer film of aluminum and molybdenum, a gate electrode D of the TFT by photoetching, and scanning lines Xn, Xn +1..., The formation process of the auxiliary capacitance electrode 14, the gate insulating film 13,
Step of forming a semiconductor layer and ohmic contact layer made of a-Si or p-Si, step of forming semiconductor layer 22 by photoetching, 3 of molybdenum / aluminum / molybdenum
A step of forming a second metal layer comprising a layer film, a source electrode S of the TFT by photoetching,
Since the drain electrode D, the signal lines Ym, Ym + 1..., And the TFT channel portion 23 are formed in substantially the same manner as the AR substrate manufacturing method of the conventional liquid crystal display device described above, The detailed explanation is omitted.

The cross-sectional view of the substrate in this state is as shown in FIG. 1, but the remaining photoresist film 30 is also shown in FIG. In the substrate in this state, the photoresist film 30 is stripped with a stripping solution in order to cover the passivation film in a subsequent process. At this time, since the photoresist film 30 may remain, the photoresist film 30 may be removed by ashing by, for example, a well-known ashing method.

Thereafter, for the purpose of uniformizing TFT characteristics and cleaning the surface of the gate insulating film 13, a dry oxidation process for exposing the channel portion 23 of the semiconductor layer 22 while oxygen or ozone gas is plasmatized by photoexcitation or high frequency. In this dry oxidation process, the TFT source electrode S, drain electrode D, signal lines Ym, Ym + 1... Metal layers are also exposed. Each of these metal layers is formed of a second metal layer composed of a three-layer film of molybdenum / aluminum / molybdenum. Since the surface is a molybdenum layer, an oxide of molybdenum is formed in this dry oxidation process. It is formed. Since this molybdenum oxide is slightly conductive, if a conductive path is formed between this molybdenum oxide and an adjacent metal layer, this portion becomes a short-circuit point, and finally In addition, a short circuit between the drain electrode D and the source electrode S of the TFT causes a bright spot defect.

In order to remove the molybdenum oxide formed in the dry oxidation treatment step and to clean other impurities, a water washing step is provided before forming a passivation film in the next step. According to the experiments by the inventors of the present application, it takes a considerable amount of time for the molybdenum oxide to be easily peeled off on the surface of the molybdenum metal after the dry oxidation treatment process is completed. In addition, molybdenum oxide was newly formed during the water washing step and the subsequent drying step, and water-drop-like soils containing molybdenum oxide in a considerable proportion were observed after the drying step.

This is because evaporation of water droplets remaining on the surface after washing with water is not performed uniformly from the surface, but is actively performed at the three-phase interface between water, metal, and the surrounding atmosphere. Molybdenum oxide, which is newly formed as it evaporates and is present in the water droplets, gradually moves to the three-phase interface and gradually concentrates at this three-phase interface. It is considered that this is recognized as water droplet-like dirt. Therefore, if the water washing step is carried out after the molybdenum oxide is completely formed after the dry oxidation treatment step, the molybdenum drops are completely contained in the water droplets remaining on the surface after the water washing even if the water washing is performed for a short time. As a result, waterdrop-like dirt is not generated, and generation of bright spot defects due to a short circuit between the drain electrode D and the source electrode S of the TFT can be suppressed.

According to the experiments by the inventors of the present application, the duration of the standing treatment after the dry oxidation treatment step so as not to cause water-drop-like contamination caused by molybdenum oxide after washing is not sufficient for 30 minutes. If left standing for a longer time, the generation of water droplets caused by molybdenum oxide is reduced in proportion to the duration of the standing treatment, and it is substantially caused by molybdenum oxide after 60 minutes. It has been found that the water-drop-like stains can no longer be seen. In this case, when the variation is taken into consideration, the standing treatment process is sufficient if it is 60 minutes to 90 minutes.

In this way, if the duration of the neglecting process is increased, the molybdenum oxide generated on the surface of the molybdenum metal is easily separated in proportion to it, and it is sufficiently washed away even in a short cleaning process. Will not occur. Note that the inventors of the present application set the duration of the neglected treatment process to at least 2 hours in consideration of safety in order to further reduce the probability of occurrence of a short circuit between the drain electrode D and the source electrode S of the TFT.

Therefore, if a passivation layer 19 (see FIG. 3; the same applies hereinafter) made of silicon nitride or silicon oxide is formed on the entire substrate by plasma CVD or the like in the subsequent process, the source electrode S, drain electrode D, signal line Ym, Ym + 1,..., TFT channel portion 23 is protected by passivation layer 19, so that formation of interlayer film 20 over the entire display region, formation of contact hole 18, and ITO, etc. on the surface of passivation layer 19 thereafter IZ
Even after passing through the pixel electrode 12 step made of a transparent conductive material such as O, these steps no longer cause bright spot defects due to a short circuit between the drain electrode D and the source electrode S of the TFT due to the oxide of molybdenum. Become irrelevant. Therefore, according to the manufacturing method of the present invention, the short circuit between the drain electrode D and the source electrode S of the adjacent TFT due to the molybdenum oxide is eliminated, and the defects of the active matrix display device are reduced.

It is sectional drawing of the part corresponding to the AA line of FIG. 2 in the manufacturing process of the array board | substrate of a liquid crystal display device. FIG. 10 is a plan view of several pixels that are seen through a color filter substrate of a conventional active matrix liquid crystal display device. It is AA sectional drawing of FIG. FIG. 3 is a schematic enlarged view of a portion B in FIG. 2.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Liquid crystal display device 11 1st translucent board | substrate 12 Pixel electrode 13 Gate insulating film 14 Auxiliary capacitance electrode 15 2nd translucent board | substrate 18 Contact hole 19 Passivation layer 20 Interlayer film 22 Semiconductor layer 23 Channel part 25 Water droplet-like Dirt Xn, Xn + 1 ... Scanning line Ym, Ym + 1 ... Signal line

Claims (4)

(1) forming a metal layer having at least a surface layer of molybdenum after forming a semiconductor layer on the surface of the gate insulating film;
(2) forming a photoresist layer having a predetermined pattern on the surface of the metal layer and then etching the metal layer to form a channel portion, a source electrode, a drain electrode, and a signal line of a thin film transistor;
(3) removing the photoresist;
(4) water washing step,
(5) laminating a passivation layer on the surface including the metal layer;
In an active matrix display device manufacturing method including:
An active matrix display comprising a step of performing a dry oxidation process on a part of the channel portion of the thin film transistor and then leaving it for a predetermined time between the steps (3) and (4). Device manufacturing method. 2. The method of manufacturing an active matrix display device according to claim 1, wherein the step of performing the dry oxidation process is a photo-excited oxidation process or a plasma oxidation process using oxygen or ozone gas. 2. The method of manufacturing an active matrix display device according to claim 1, wherein the passivation layer is made of silicon nitride. 4. The method of manufacturing an active matrix display device according to claim 1, wherein the predetermined time is 60 minutes or more.

Images