JP2010181839A - Method of manufacturing display device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To manufacture a display device which can suppress the corrosion of an Al alloy film and is reduced in contact electric resistance with a transparent conductive film. <P>SOLUTION: The Al alloy film is directly brought into contact with the transparent conductive film according to the following processes (1) to (4) in this order: (1) a first process of forming the Al alloy film containing a metal element which is more noble than Al, (2) a second process of forming a contact hole by photolithography and dry etching, (3) a third process of performing stripping of a photo resist produced by the photolithography, and (4) a fourth process of forming the transparent conductive film. The second process includes a process of controlling a flow ratio of gases at over-etching into 30% or lower in the rate of SF<SB>6</SB>/(SF<SB>6</SB>+O<SB>2</SB>) and covering the surface of the Al alloy film with an oxide of Al, and the third process includes a process of bringing the Al alloy film to contact with an alkaline solution of a pH of 10.5 or higher to remove the oxide of Al. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a method for manufacturing a display device used for a liquid crystal display, a semiconductor device, an optical component, and the like. Specifically, the present invention is an improvement of direct contact technology in which an Al alloy film and a transparent conductive film are in direct contact, and a contact hole for electrically connecting the Al alloy film and the transparent conductive film through an insulating film is provided. The present invention relates to a method capable of manufacturing a display device having a low contact electric resistance without corroding an Al alloy film.

  Al alloys are used in the field of thin display devices (FPD) such as liquid crystal display devices, plasma display devices, electroluminescence display devices, and field emission display devices because of their low electrical resistivity and ease of processing. It is used as a thin film material for films, electrode films, and reflective electrode films.

  For example, as shown in FIG. 1, an active matrix liquid crystal panel includes a thin film transistor (TFT) 4 that is a switching element, a pixel electrode 5 made of an oxide transparent conductive film such as an indium tin oxide (ITO) film, And a TFT substrate 1 having a wiring portion 6 including scanning lines and signal lines. The Al alloy is used as a wiring material constituting the scanning lines and signal lines. The Al alloy film and the pixel electrode (transparent conductive film) 5 of the wiring part 6 including the scanning lines and signal lines are usually electrically connected through a contact hole of an insulating film provided therebetween.

  Conventionally, when various electrode portions formed by an Al alloy film are brought into direct contact with the pixel electrode, insulating aluminum oxide or the like is formed at the interface to increase the contact electric resistance. A barrier metal layer made of a refractory metal such as Mo, Cr, Ti, or W is formed between the film and the film.

  However, since the formation of the barrier metal layer leads to an increase in manufacturing cost and a decrease in productivity, a technique (direct contact technique) is proposed in which the formation of the barrier metal layer is omitted and the Al alloy film is brought into direct contact with the pixel electrode. (For example, see Patent Document 1 and Patent Document 2). In these patent documents, if an Al alloy film containing a predetermined alloy element is used, the contact resistance with the pixel electrode can be reduced even if the barrier metal layer is omitted, and further, the electric resistance of the Al alloy itself can be reduced. It is disclosed that an improvement in heat resistance can also be achieved.

A structure in which the Al alloy film and the transparent conductive film are electrically connected through a contact hole formed on the insulating film is formed by, for example, the steps shown in FIGS. That is, as shown in FIG. 3, an Al alloy film is formed by sputtering or the like and patterned to form the drain electrode 29 (see FIG. 7). Next, for example, an insulating film (SiN _X insulating film) 30 is formed by plasma CVD, and a photoresist (photosensitive resin) 31 is further formed thereon, and an opening of the photoresist 31 is etched. A contact hole 32 is formed in the insulating film 30 as shown in FIG. After the contact hole 32 is formed, the photoresist 31 is removed with a stripping solution as shown in FIG. 9, and then a transparent conductive material such as an indium tin oxide (ITO) film is formed on the insulating film 30 as shown in FIG. By forming the film 5, a structure in which the Al alloy film and the transparent conductive film are in direct contact is obtained.

JP 2004-214606 A JP 2006-261636 A

  As disclosed in Patent Document 1 and Patent Document 2, various functions are imparted by adding a predetermined alloy element to Al, but there is an unfavorable tendency that corrosion resistance deteriorates due to the addition of the alloy element. appear.

  For example, in the manufacturing process of the array substrate, a plurality of wet processes are passed. However, when a metal nobler than Al is added, a problem of galvanic corrosion appears and the corrosion resistance deteriorates. For example, in the photolithography process, an alkaline developer containing TMAH (tetramethylammonium hydroxide) is used. However, in the case of a direct contact structure, the barrier metal layer is omitted, and the Al alloy film is exposed, which is caused by the developer. It becomes easy to receive damage.

  Further, in the cleaning step of removing the photoresist (resin) formed in the photolithography step, water washing is continuously performed using an organic stripping solution containing amines. However, when an amine and water are mixed, an alkaline solution is formed, which causes another problem that Al is corroded in a short time. By the way, Al alloy has received the thermal history by passing through a CVD process before passing through a peeling cleaning process. In the course of this thermal history, the alloy component forms precipitates (high resistance Al oxide) in the Al matrix, so that the contact electrical resistance increases when the Al alloy film is brought into direct contact with the pixel electrode of the transparent conductive film. . In addition, since there is a large potential difference between the precipitate and Al, the alkali corrosion proceeds by the galvanic corrosion at the moment when the amine, which is the stripping solution, comes into contact with water, and the electrochemically basic Al ionizes. And pit-like pitting corrosion (black spots) is formed. In particular, when the Al alloy film is immersed in a weak alkaline solution having a pH of about 8.5 to 10, a battery reaction occurs between the deposited Al oxide and the Al alloy film, and partial corrosion occurs.

  The present invention has been made in view of such circumstances, and an object thereof is to form an Al alloy film in direct contact with the transparent conductive film on the substrate, and the Al alloy film and the transparent conductive film are electrically connected. An object of the present invention is to provide a method for manufacturing a display device having a contact hole connected to the substrate, in which corrosion of the Al alloy film can be suppressed and contact electric resistance with a transparent conductive film is also reduced.

In the method for manufacturing a display device according to the present invention, which has achieved the above-described problem, an Al alloy film that is in direct contact with a transparent conductive film is formed on a substrate, and the Al alloy film and the transparent are interposed via an insulating film. A manufacturing method of a display device having a contact hole for electrically connecting a conductive film, wherein the Al alloy film is brought into direct contact with the transparent conductive film by the following steps (1) to (4) Is.
(1) a first step of forming an Al alloy film containing a metal element nobler than Al;
(2) a second step of forming a contact hole by photolithography and dry etching;
(3) a third step of removing the photoresist generated by photolithography, and (4) a fourth step of forming a transparent conductive film;
In this order,
The second step is a step of covering the surface of the Al alloy film with an Al oxide by controlling the gas flow ratio in over-etching to 30% or less by the ratio of SF ₆ / (SF ₆ + O ₂ ). Including
The third step includes a step of removing the Al oxide by contacting with an alkaline solution having a pH of 10.5 or more.

In a preferred embodiment, the second step includes a step of performing oxygen ashing after overetching to cover the surface of the Al alloy film with an oxide of Al. The gas flow rate ratio in the overetching is SF _6. The third step in which the ratio of / (SF ₆ + O ₂ ) is 65% or less further includes a step of performing oxygen ashing after the overetching.

  In a preferred embodiment, the third step includes a step of removing the Al oxide by contacting with an alkaline solution having a pH of less than 10.5 and then contacting with an alkaline solution having a pH of 10.5 or more.

  In a preferred embodiment, the third step further includes a water washing step after the resist stripping.

  In a preferred embodiment, the Al alloy film in the first step contains at least one element selected from the group consisting of Ni, Co, Ag, Au, Zn, Cu, and Ge.

  In a preferred embodiment, the Al alloy film further contains one or more rare earth elements at a ratio of 0.1 to 0.5 atomic%.

  In the present invention, (a) overetching for contact hole formation (and oxygen ashing if necessary) is controlled, and Al oxide film is actively generated on the Al alloy film surface. Corrosion of the alloy film can be effectively prevented, and (a) since the Al oxide is completely removed by subsequent appropriate wet etching, the contact electric resistance between the Al alloy film and the transparent conductive film is reduced. Can be reduced. Therefore, according to the present invention, a low contact electric resistance can be stably realized for a long period of time while preventing the corrosion of the Al alloy film, and thus a highly reliable display device can be provided.

FIG. 1 is an enlarged schematic cross-sectional explanatory view showing the structure of a typical liquid crystal panel applied to an active matrix liquid crystal display device. FIG. 2 is a schematic cross-sectional explanatory view illustrating the configuration of a thin film transistor (TFT) applied to an array substrate for a display device. FIG. 3 is an explanatory diagram showing an example of a manufacturing process of the display device array substrate shown in FIG. 2 in order. FIG. 4 is an explanatory diagram showing an example of a manufacturing process of the display device array substrate shown in FIG. 2 in order. FIG. 5 is an explanatory diagram showing an example of a manufacturing process of the display device array substrate shown in FIG. 2 in order. FIG. 6 is an explanatory diagram showing an example of the manufacturing process of the display device array substrate shown in FIG. 2 in order. FIG. 7 is an explanatory diagram showing an example of a manufacturing process of the display device array substrate shown in FIG. 2 in order. FIG. 8 is an explanatory diagram showing an example of a manufacturing process of the display device array substrate shown in FIG. 2 in order. FIG. 9 is an explanatory diagram showing an example of a manufacturing process of the display device array substrate shown in FIG. 2 in order. FIG. 10 is an explanatory diagram showing an example of the manufacturing process of the display device array substrate shown in FIG. 2 in order. FIG. 11 is a schematic diagram of a manufacturing process of an experimental display device in the example. FIG. 12 is a schematic diagram of a manufacturing process of an experimental display device in the example. FIG. 13 is a TEM image of an Al surface oxide film (AlOx) according to an example of the present invention. FIG. 14 is a TEM image of the Al surface oxide film (AlOx) of the comparative example.

  The present invention provides a direct contact technique in which an Al alloy film containing a metal element nobler than Al (hereinafter sometimes simply referred to as “Al alloy film”) and a transparent conductive film directly contact each other on a substrate of a display device. In a display device having a contact hole in which an Al alloy film and a transparent conductive film are electrically connected via an insulating film, the corrosion prevention of the Al alloy film and the contact electricity between the Al alloy film and the transparent conductive film The present invention relates to a method for manufacturing a display device that can satisfy a reduction in resistance (hereinafter, sometimes simply referred to as “contact electrical resistance”).

  In order to provide a manufacturing method that can effectively prevent black spots generated in the stripping of the photoresist and subsequent cleaning processes, etc. while maintaining a low contact electric resistance in the display device having the above-described configuration, It has been repeated. As a result, in the process procedure until the Al alloy film is brought into direct contact with the transparent conductive film, surprisingly, an Al oxide that adversely affects the reduction of the contact electric resistance is applied to the surface of the Al alloy film for a certain period of time. It has been found that the generation of black spots is remarkably suppressed when actively generated. Specifically, after a contact hole is formed in an interlayer insulating film such as silicon nitride (SiNx) by photolithography and dry etching, before the photoresist generated by photolithography is removed (that is, the contact hole is formed in the insulating film) Thereafter, it was found that the surface of the Al alloy film may be subjected to a treatment for oxidizing the surface of the Al alloy film before the photoresist is peeled off and covered with an oxide of Al (AlOx) (see Examples described later). Furthermore, if the step of removing the AlOx by removing (cleaning) the AlOx by contacting (immersing) it in a strong alkaline solution having a pH of at least 10.5 in the photoresist peeling / cleaning step, the contact electric resistance can be simultaneously reduced. (See Examples below).

  Furthermore, in order to efficiently generate the Al oxide (AlOx), it is effective to perform ion bombardment of oxygen ions at the time of “after contact hole formation of the insulating film and before resist removal” described above. I found out. Specifically, in overetching after dry etching (continuous etching after removing the insulating film), or overetching and subsequent oxygen ashing (ashing using oxygen plasma), the gas flow rate ratio in the overetching (fluorine) We have found that the desired AlOx useful for preventing sunspots can be obtained by properly controlling the flow rate of the mixed gas of the system gas and oxygen gas and controlling the RF power and processing time in oxygen ashing. did.

  Hereinafter, the background of the above knowledge and the characteristic part of the present invention will be described in detail.

  As described above, when the ITO film constituting the transparent conductive film is formed on the Al alloy film constituting the drain electrode by sputtering or the like, an oxide film (AlOx) is formed at the interface between the Al alloy film and the transparent conductive film. And the contact electrical resistance is increased. Therefore, until now, in the initial stage of ITO film formation, measures have been taken to oxidize the surface of the Al alloy film as much as possible. For example, in an atmosphere without oxygen addition, a film thickness of about 5 to 20 nm (preferably An ITO film having a thickness of about 10 nm was formed. However, since a film forming process of a display device passes through a plurality of wet processes, the use of an Al alloy film containing a metal that is nobler than Al such as Ni or Cu causes the above-described problem of galvanic corrosion, resulting in corrosion resistance. Will deteriorate. For example, when forming a contact hole in an insulating film, the insulating film is usually patterned on the Al alloy film by photolithography and dry etching (contact etching) is performed to form a contact hole. The resist is stripped using a stripping solution (typically, “TOK106” and “PRS2000” manufactured by Tokyo Ohka Kogyo Co., Ltd.). In the water rinse (cleaning step) after stripping the resist, the water-soluble liquid is It becomes an alkaline solution, and corrosion (partial corrosion) occurs between the matrix aluminum and the intermetallic compound in the pH 8.5 to 10 region, and black spots are generated.

  On the other hand, in the present invention, (a) over-etching in which the flow ratio of the mixed gas is appropriately controlled is performed at a predetermined time “after contact hole formation and before photoresist removal”, or (a) When oxygen ashing is performed after overetching, the surface of the Al alloy film is subjected to “AlOx generation processing” in which the flow rate ratio of the mixed gas at the time of overetching and the RF power at the time of oxygen ashing are appropriately controlled. Is actively oxidized and covered with AlOx. Therefore, according to the method of the present invention, even when the Al alloy film is exposed to the above alkaline solution, occurrence of partial corrosion of the Al alloy film is suppressed.

  Furthermore, in the present invention, after the above steps, in the resist peeling / cleaning step, the step of wet etching the surface of the Al alloy film by being brought into contact with a strong alkaline solution having a pH of 10.5 or more is necessarily performed. AlOx is completely removed. Therefore, even when the Al alloy film and the transparent conductive film are brought into direct contact by subsequent formation of the transparent conductive film, a high-resistance Al oxide that causes an increase in contact electric resistance is hardly formed. In addition, according to the present invention, since a conductive precipitate containing a metal element nobler than Al is formed at the interface with the transparent conductive film, a decrease in contact resistance can be suppressed.

  As described above, the method of the present invention can reduce the contact electric resistance by “AlOx generation treatment for preventing black spot generation” and “photoresist peeling / cleaning step” before “photoresist peeling after contact hole formation”. The characteristic feature is that by performing both of the wet etching treatment with a strong alkaline solution for the purpose of "reducing the corrosion of the Al alloy film and reducing the contact electrical resistance". In particular, the method of the present invention should be excluded from the viewpoint of reducing the contact electrical resistance, and Al oxide (AlOx), for which measures for suppressing the generation thereof have been taken as much as possible, is referred to as “improvement of corrosion resistance. From the point of view, it was completed based on the idea of reversal (ideology) that it should rather be generated and used effectively at a predetermined time. Furthermore, according to the method of the present invention, preferably, a relatively small amount of a contact resistance reducing element such as Ni, Co, Cu, Ge or the like is added, so that the above action is further promoted.

  Each step forming the characteristic part of the present invention will be described in more detail.

  First, in forming the AlOx by oxidizing the Al alloy film before the above “contact hole formation and before resist stripping”, it is effective to ion bombard oxygen ions, and reactive ion etching (REACTIVE ION ETCHING). , RIE) method, ion bombardment is preferably performed. As a result, disconnection of the Al alloy film wiring around the contact hole and a decrease in adhesion can be avoided, and a dense film can be easily formed to improve the corrosion prevention effect.

  Specifically, the control conditions are slightly different between the case where only over-etching after removing the insulating film is performed and the case where oxygen ashing is performed after over-etching, and will be described separately below.

(A) When only over-etching is performed (no subsequent oxygen ashing)
In the above embodiment, a mixed gas of fluorine-based gas (for example, SF ₆ ) and oxygen gas is used, and the flow rate ratio is controlled to 30% or less by the ratio of SF ₆ / (SF ₆ + O ₂ ) to perform over-etching. Do. As a result, AlOx effective for preventing black spots is generated with a predetermined thickness (preferably about 4 nm or more). From the standpoint of preventing sunspots, the flow rate ratio of SF ₆ / (SF ₆ + O ₂ ) is preferably as small as possible, and is preferably about 10% or less. The lower limit of the flow rate ratio is not particularly limited from the viewpoint of preventing blackness, but is preferably about 5% or more from the viewpoint of removing SiN residue as an insulating film.

The gas (mixed gas) used for over-etching only needs to contain at least a fluorine-based gas such as SF ₆ and an oxygen gas, and may further contain an inert gas such as He or Ar. In any case, the flow rate ratio of the fluorine-based gas (SF ₆ ) in the total mixed gas only needs to be controlled within the above range.

  In the over-etching, conditions other than those described above are not particularly limited. For example, the pressure may be controlled to about 10 Pa and RF power to about 50 W.

(B) When performing oxygen ashing after over-etching In the above embodiment, first, over-etching is performed by controlling the flow rate ratio of the mixed gas during over-etching to 65% or less by the ratio of SF ₆ / (SF ₆ + O ₂ ). To do. Here, since oxygen ashing is performed thereafter, the upper limit of the flow rate ratio can be set higher than in the case of (A) described above. The smaller the above flow rate ratio, the better, and it is generally preferable that the flow rate ratio is 50% or less.

  The overetching conditions are the same as in the case of (A) except that the upper limit of the flow rate ratio is different.

Thereafter, oxygen ashing is performed. Oxygen ashing means ashing by oxygen plasma and is usually performed for the purpose of removing a damaged layer on the resist surface by dry etching. In order to effectively generate AlOx useful for preventing the generation of black spots, the RF power in oxygen ashing is preferably as high as possible and as long as possible. For example, the following control is preferable.
RF power: preferably 50 W or more, more preferably 100 W or more.
Oxygen ashing time: preferably 1 minute or longer, more preferably 3 minutes or longer.

  Conditions other than those described above for oxygen ashing are not particularly limited, and conditions that are usually performed can be appropriately selected and employed.

According to the above method, AlOx is formed so as to cover the surface of the Al alloy film. The thickness of the AlOx is preferably about 4 nm or more, which can effectively prevent the generation of black spots (see Examples described later). In order to effectively exhibit the above action, the thickness of AlOx is better as it is thicker, and is more preferably about 5 nm or more. The upper limit of AlOx is preferably about 20 nm or less considering the ease of removal by contact with the subsequent alkaline solution. The thickness of AlOx was determined by cross-sectional TEM observation using “FE-TEM HF-2000” manufactured by Hitachi, Ltd.

  Next, the photoresist is peeled off and washed. In the above process, in the present invention, it is indispensable to perform contact (wet etching) with at least an alkaline solution having a pH of 10.5 or higher, thereby completely removing AlOx produced by the above-described process (total corrosion, film Will be reduced). As a result, a low contact electric resistance is stably ensured for a long time without causing partial corrosion of the Al alloy film. That is, as demonstrated in the examples to be described later, even if wet etching with a weak alkaline solution having a pH of less than 10.5 (pH 9.5 in the examples) is performed under various immersion conditions, the contact electric resistance is not sufficient. No reduction effect was obtained, and the desired low contact electric resistance could be achieved only when wet etching with strong alkali having a pH of 10.5 or higher was performed as specified in the present invention. From the viewpoint of reducing the contact electric resistance, the higher the pH of the alkaline solution, the better. However, if the pH is too high, the film thickness of AlOx becomes too large, and the transparent conductive film such as ITO to be formed later In order to cause disconnection, the pH is preferably about 13 or less. Specifically, for example, an aqueous sodium hydroxide solution having the above pH can be used. Commercially available products may be used as the above alkaline solution. For example, as a TMAH solution having a pH of about 12.5 used as a developer, “NMD-W” manufactured by Tokyo Ohka, “AZ-” manufactured by AZ Electronic Materials, Inc. 300 MIF ”; an aqueous solution of a resist stripping solution“ TOK106 ”(manufactured by Tokyo Ohka Kogyo Co., Ltd.) having a pH of about 10.5 to 13; an aqueous solution of“ PRS2000 ”having a pH of about 10.5 to 13 manufactured by Dongwoo Finechem, etc. Is done. The above “TOK106” and “PRS2000” are a mixed solution of monoethanolamine and dimethylsulfoxide (DMSO), and the pH range can be adjusted by the mixing ratio thereof. The preferred temperature and time for wet etching may be appropriately determined according to the alkaline solution used or the composition of the Al alloy, etc., so that AlOx is appropriately removed. It is preferably 180 seconds (preferably, 10 to 120 seconds at 30 to 60 ° C.).

  In the present invention, it is only necessary to perform at least “contact treatment with a strong alkaline solution having a pH of 10.5 or more (wet etching treatment)” in the removal and cleaning of the photoresist, as long as the effects of the present invention are not impaired. The above process may be further included. For example, after performing the wet etching process with a weak alkali solution having a pH of less than 10.5, the wet etching process with a strong alkali having a pH of 10.5 or more may be performed. Processing is also included within the scope of the present invention. In the examples described below, the pH 12.8 TMAH solution is immersed after the immersion of the pH 9.5 TMAH solution. However, in the above method, the “treatment with a strong alkali solution” defined in the present invention is performed to form AlOx. Since it is completely removed, the desired effect is effectively exhibited. The wet etching treatment with the weak alkali solution may be appropriately performed according to the “wet etching treatment with the strong alkali solution” or the composition of the Al alloy film as long as the effect of the present invention is not impaired. It is preferable to carry out a weak alkaline solution of about 5 to 10 at about 30 to 60 ° C. for about 10 to 300 seconds.

  In the above step, it is preferable to further perform washing with water (cleaning rinse). Thereby, since the solution such as the resist stripping solution is brought into the cleaning tank, for example, various alkaline aqueous solutions having a pH of about 9.5 to 13 can be obtained, and the corrosion partially generated in the Al alloy film can be completely suppressed. Become.

  The process characterizing the present invention has been described above.

  The present invention is particularly characterized in that the above steps are controlled, and a commonly used method can be appropriately employed for the other steps.

  In this specification, “a metal element nobler than Al” means a metal element having a smaller ionization tendency than Al. Further, in this specification, the “photolithography method” means a method of forming a pattern by irradiating a photoresist (including both negative and positive photoresists) with light and developing, and then etching.

  Hereinafter, details of the method of the present invention will be described in the order of steps with reference to the drawings. Since the characterizing portion of the present invention has been described in detail above, the following description will focus on other steps.

  First, a method for manufacturing the TFT array substrate 1 shown in FIG. 2 will be briefly described. Here, an example of the thin film transistor formed as the switching element is an amorphous silicon TFT using hydrogenated amorphous silicon as a semiconductor layer.

  First, an Al alloy film (for example, Al-0.6 atomic% Ni-0.5 atomic% Cu-0.3 atomic% La) having a film thickness of about 200 nm is formed on the glass substrate 1a by a technique such as sputtering, By patterning the Al alloy film, the gate electrode 26 and the scanning line 25 are formed (FIG. 3). At this time, it is preferable to etch the peripheral edge of the aluminum alloy thin film into a taper of about 30 to 40 ° so that the coverage of the gate insulating film 27 described later is improved. Next, as shown in FIG. 4, a gate insulating film 27 is formed of a silicon oxide film (SiOx) having a film thickness of, for example, about 300 nm by a method such as plasma CVD, and further hydrogenation having a film thickness of, for example, about 50 nm. An amorphous silicon film (a-Si: H) and a silicon nitride film (SiNx) having a thickness of about 300 nm are formed.

Subsequently, as shown in FIG. 5, the silicon nitride film (SiNx) is patterned by backside exposure using the gate electrode 26 as a mask to form a channel protective film. Further, an n ⁺ -type hydrogenated amorphous silicon film (n ⁺ a-Si: H) having a thickness of, for example, about 50 nm doped with phosphorus is formed thereon, and then, as shown in FIG. a-Si: H) and an n ⁺ -type hydrogenated amorphous silicon film (n ⁺ a-Si: H) are patterned.

Then, an Al alloy film having a thickness of, for example, about 300 nm is formed thereon, and patterned as shown in FIG. 7, so that the source electrode 28 integrated with the signal line and the drain electrode in contact with the transparent conductive film 5 are formed. 29 is formed. Further, the n ⁺ type hydrogenated amorphous silicon film (n ⁺ a-Si: H) on the channel protective film (SiNx) is removed using the source electrode 28 and the drain electrode 29 as a mask.

Then, as shown in FIG. 8, a protective film is formed by forming a silicon nitride film 30 with a film thickness of, for example, about 300 nm using, for example, a plasma CVD apparatus. The film formation at this time is performed at about 260 ° C., for example. Then, after a photoresist layer 31 is formed on the silicon nitride film 30, the silicon nitride film 30 is patterned, and contact holes 32 are formed in the silicon nitride film 30 by, for example, dry etching. Although not shown, a contact hole is formed at a portion corresponding to connection with TAB on the gate electrode at the end of the panel at the same time. In the present invention, the conditions for this dry etching are not particularly limited, and the conditions usually used can be appropriately employed. As described above, the present invention generates AlOx useful for preventing blackness by appropriately controlling the conditions of overetching (and oxygen ashing) after dry etching. As an example of preferable conditions for dry etching, a mixed gas of SF ₆ and O ₂ is used, and the flow rate ratio of SF ₆ / (SF ₆ + O ₂ ) is controlled to about 10% and the RF power is controlled to about 50 W. The

  Next, over-etching after dry etching is appropriately controlled as described above for the purpose of oxidizing the Al alloy film and generating AlOx useful for preventing black spots. The details are as described above, whereby the surface of the Al alloy film is covered with AlOx (not shown).

  Further, as shown in FIG. 9, an ashing process using oxygen plasma is performed under the above-described conditions as necessary. This oxygen ashing process is not essential, and only the over-etching described above may be performed. Thereafter, the photoresist layer 31 is stripped using, for example, an amine-based stripping solution, and finally an ITO film having a thickness of, for example, about 40 nm is formed as shown in FIG. The transparent conductive film 5 is formed by patterning. At the same time, when an ITO film is patterned for bonding to the TAB at the connection portion of the gate electrode at the edge of the panel, the TFT array substrate is completed.

  The Al alloy used in the present invention contains a noble metal element (an element having a smaller ionization tendency than Al), preferably Ni, Co, Ag, Au, Zn, Cu, And at least one element selected from the group consisting of Ge. These elements contribute to the reduction of contact resistance. In the present invention, these elements can be used alone or in combination of two or more. Preferred metal elements are Ni, Co, Ag, and Zn, and more preferably Ni, Co, and Ag.

  The content (total) of the metal elements is preferably about 0.1 to 1.0 atomic% in the Al alloy film. When the content of the metal element is less than 0.1 atomic%, the contact electric resistance is decreased. On the other hand, when the content of the metal element exceeds 1.0 atomic%, the electrical resistance of the Al alloy film itself increases. The more preferable content of the metal element is 0.2 atomic% or more and 1.0 atomic% or less.

  It is also effective to further include one or more rare earth elements as the metal element (alloy element) other than the above in the Al alloy film of the present invention. These elements preferably have an effect of increasing heat resistance to 300 ° C. or more and increasing mechanical strength, corrosion resistance, etc. by containing 0.1 to 0.5 atomic% in the Al alloy film. Any of the lanthanoid series rare earth elements can be adopted as such a metal, but at least one selected from the group consisting of La, Gd, and Nd is particularly preferable.

  If a display device including a TFT array substrate formed in this way is used as, for example, a liquid crystal display device, the contact electrical resistance between the transparent conductive film and the connection wiring portion can be minimized, The adverse effect on the display quality of the display screen can be suppressed as much as possible.

  Hereinafter, the present invention will be described in more detail with reference to examples. However, the present invention is not limited by the following examples, and is implemented with appropriate modifications within a range that can meet the purpose described above and below. Of course, any of these is also included in the technical scope of the present invention.

(Production of experimental display device)
FIG. 11 and FIG. 12 are schematic diagrams of manufacturing steps of the experimental display device used in this example. The structure of the experimental display device is a reproduction of the Al alloy film, the interlayer insulating film 30, the contact hole 32, and the photoresist 31 used as the drain electrode 29 shown in FIGS. Etc. are not produced.

  First, as shown in FIG. 11, assuming an alkali-free glass plate (plate thickness 0.7 mm) as a substrate and assuming a drain electrode on its surface, Al-0.6 atomic% Ni-0.5 atomic% Cu A −0.3 atomic% La alloy film 72 was formed by sputtering (thickness: 300 nm). Next, patterning was performed by photolithography and dry etching, and the Al alloy thin film 72 was etched into a taper shape of about 30 ° to 40 °.

  A silicon nitride (SiNx) film was formed thereon as the insulating film 73 by a plasma vapor deposition method (CVD method) (thickness 300 nm). The film formation temperature at this time was 250 ° C., and the film formation time was about 6 minutes.

A thick photosensitive resin (photoresist, novolac resin) 74 is coated on the surface of the insulating film 73 as an etching mask, and patterning is performed by photolithography and dry etching. A contact hole (contact area 10 μm × 10 μm) 75 was formed (see FIG. 11). Dry etching was performed by RIE (reactive ion etching), and the gas used was a mixed gas of SF ₆ : 33.3%, O ₂ : 26.7%, and Ar: 40%.

  After silicon nitride is dry-etched in this manner, the photoresist is removed by performing over-etching (oxygen ashing if necessary) → wet etching with an alkali solution by the following methods (1) to (4) ( (See FIG. 12). Then, after storing for 8 hours in a clean room controlled at a temperature of about 25 ° C. and a humidity of about 50%, an ITO film having a thickness of 200 nm was formed on the surface of the Al alloy film by sputtering (not shown).

In the following methods (1) to (4), (1) and (3), (2) and (4) correspond to each other, and a strong alkali treatment was performed after (1) (3 ); (2) was followed by strong alkali treatment (4). These are outlined below.
Method (1): Over etching (no oxygen ashing) → Wet etching with weak alkali (3) Method: Wet etching with strong alkali after (1) above Method (2): Over Etching (with oxygen ashing) → Wet etching with weak alkali (4) Method ... After (2) above, wet etching with strong alkali

  Hereinafter, each method will be described in detail.

(1) Over etching (no oxygen ashing) → Wet etching with weak alkali (see Table 1)
First, overetching was performed using a mixed gas of SF ₆ and O ₂ . As shown in Table 1, the flow ratio [SF ₆ / (SF ₆ + O ₂ )] of the mixed gas was changed in the range of 10 to 65%. The over-etching conditions other than the above were a pressure of about 10 Pa and an RF power of about 50 W.

  Table 2 shows the thickness of the Al oxide film (AlOx) formed on the surface of the Al alloy film (before weak alkali treatment) after overetching under each condition. For reference, TEM images of AlOx (3,000,000 times) are shown in FIG. 13 (film thickness 3.9 nm, comparative example) and FIG. 14 (film thickness 4.9 nm, example of the present invention), respectively. .

  Next, the Al thin film surface was wet-etched with a weak alkaline solution having a pH of 9.5 (an aqueous solution of “PRS2000” manufactured by Dongwoo Finechem, Inc. was used as the TMAH solution). As shown in Table 1, the wet etching time was changed between 1 and 15 minutes.

(2) Overetching (with oxygen ashing) → Wet etching treatment with weak alkali (see Table 3)
In the method (1) above, except that the flow rate ratio [SF ₆ / (SF ₆ + O ₂ )] of the mixed gas of SF ₆ and O ₂ is constant at 50% as shown in Table 3, Overetch etching was performed in the same manner as in 1). Subsequent oxygen ashing was performed by changing the RF power and processing time as shown in Table 3. The oxygen ashing conditions other than those in Table 3 were set to a pressure of about 10 Pa and an RF power of about 50 W.

  Table 4 shows the thickness of the Al oxide film (AlOx) formed on the surface of the Al alloy film after overetching → oxygen ashing under each condition (before the weak alkali treatment).

  Next, in the same manner as in the above (1), wet etching was performed with a weak alkaline solution having a pH of 9.5. As shown in Table 2, the wet etching time was changed between 1 and 15 minutes.

(3) Over-etching (no oxygen ashing) → Wet etching with weak alkali → Wet etching with strong alkali (see Table 5)
After performing the above step (1), the Al thin film surface was wet etched with a strong alkaline solution having a pH of 12.8 (using an aqueous solution of “PRS2000” manufactured by Dongwoo Finechem as the TMAH solution) (wet etching time was 25). Seconds).

(4) Overetching (with oxygen ashing) → Wet etching treatment with weak alkali → Wet etching treatment with strong alkali (see Table 6)
After performing the step (2), the Al thin film surface was wet etched with a strong alkaline solution having a pH of 12.8 used in the step (3) (wet etching time was 25 seconds).

  About each said sample, the contact electrical resistance of ITO film | membrane (transparent conductive film) and Al alloy film was measured by the 4-terminal Kelvin method. In this example, a contact electric resistance of 300Ω or less was regarded as acceptable.

  Further, the 10 μm □ contact hole was observed with a 1000 × optical microscope, and the number of black spots was measured. Depending on the number of black spots, evaluation was made with ◯ (0), Δ (1 to 10), and × (10 or more). In this example, “◯” or “Δ” was regarded as acceptable (the effect of preventing corrosion of the Al alloy film).

  These results are also shown in Tables 1, 3, 5, and 6. In the table, the unit of contact electric resistance is Ω.

  First, reference is made to Table 1 and Table 3 where the above methods (1) and (2) were performed.

  As in the above method, in the case where the wet etching with the strong alkaline solution defined in the present invention is not performed in the photoresist peeling / cleaning step, the present invention is applied in any case regardless of the treatment time of the weak alkaline solution. The low contact electric resistance set in step 1 could not be obtained. From this, it was confirmed that AlOx that brings about an increase in the contact electric resistance cannot be completely removed by the immersion treatment with the weak alkaline solution. As for the contact electrical resistance, a decrease (◯ or Δ) in the number of sunspots was observed in an example in which overetching or oxygen ashing was performed under the conditions specified in the present invention.

  Next, reference is made to Table 5 and Table 6 in which the above methods (3) and (4) were performed.

  In these methods, since wet etching with a strong alkali solution was performed, reduction of contact electric resistance was recognized in all examples. Among these, in the example in which over-etching (and oxygen ashing) is performed under the conditions specified in the present invention, the number of black spots is also suppressed, and both the corrosion prevention of the Al alloy film and the reduction of the contact electric resistance are realized. I was able to.

1 TFT array substrate 1a Glass substrate 2 Counter substrate 3 Liquid crystal layer 4 Thin film transistor (TFT)
DESCRIPTION OF SYMBOLS 5 Transparent conductive film 6 Wiring part 7 Common electrode 8 Color filter 9 Light-shielding film 10 Polarizing plate 11 Orientation film 12 TAB tape 13 Driver circuit 14 Control circuit 15 Spacer 16 Seal material 17 Protective film 18 Diffusion film 19 Prism sheet 20 Light guide plate DESCRIPTION OF SYMBOLS 21 Reflector 22 Backlight 23 Holding frame 24 Printed circuit board 25 Scan line 26 Gate electrode 27 Gate insulating film 28 Source electrode 29 Drain electrode 30 Protective film (silicon nitride film)
31 Photoresist 32 Contact hole 71 Glass substrate 72 Al alloy film 73 Insulating film 74 Photoresist

Claims (6)

An Al alloy film that is in direct contact with a transparent conductive film is formed on a substrate, and a method of manufacturing a display device having a contact hole that electrically connects the Al alloy film and the transparent conductive film through an insulating film. And
A method for producing a display device, wherein the Al alloy film is brought into direct contact with the transparent conductive film by the following steps (1) to (4).
(1) a first step of forming an Al alloy film containing a metal element nobler than Al;
(2) a second step of forming a contact hole by photolithography and dry etching;
(3) a third step of removing and cleaning the photoresist generated by photolithography, and (4) a fourth step of forming a transparent conductive film;
In this order,
The second step is a step of covering the surface of the Al alloy film with an Al oxide by controlling the gas flow ratio in over-etching to 30% or less by the ratio of SF ₆ / (SF ₆ + O ₂ ). Including
The third step includes a step of removing the Al oxide by contacting with an alkaline solution having a pH of 10.5 or more. The second step includes a step of performing oxygen ashing after over-etching to cover the surface of the Al alloy film with an oxide of Al, and a gas flow rate ratio in the over-etching is SF ₆ / (SF ₆ + O The production method according to claim 1, wherein the ratio of ₂ ) is 65% or less.   3. The method according to claim 1, wherein the third step includes a step of removing the Al oxide by contacting with an alkaline solution having a pH of less than 10.5 and then contacting with an alkaline solution having a pH of 10.5 or more. Production method.   The Al alloy film in the first step includes at least one element selected from the group consisting of Ni, Co, Ag, Au, Zn, Cu, and Ge. Production method.   The method according to claim 4, wherein the Al alloy film further contains one or more rare earth elements at a ratio of 0.1 to 0.5 atomic%.   The manufacturing method according to claim 1, wherein the third step further includes a washing step with water after resist stripping.