JP2011112934A - Display device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a display device preventing pinhole corrosion without providing further steps for applying and peeling of a paint for corrosion prevention in the display device provided with a structure wherein a transparent conductive film and an Al alloy film are directly connected in a thin film transistor. <P>SOLUTION: In the display device provided with the structure wherein the transparent conductive film and the Al alloy film are directly connected in the thin film transistor, the Al alloy film contains ≤0.15 at% (not including 0 at%) Ni and/or Co, 0.2 to 2.0 at% Ge and 0.05 to 1.0 at% at least one element selected from a group consisting of La, Gd, Nd and Y and has the aspect ratio (a corrosion depth/a corrosion diameter) of a corrosion hole observed on the surface of the Al alloy film of 0.12 or lower. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a display device, and more particularly to a display device having a structure in which a transparent conductive film (oxide conductive film) and an Al alloy film are directly connected in a thin film transistor of the display device.

  A liquid crystal display device used in various fields ranging from a small mobile phone to a large television exceeding 30 inches uses a thin film transistor (hereinafter referred to as “TFT”) as a switching element, and a transparent pixel electrode. A TFT substrate provided with a wiring portion such as a gate wiring and a source-drain wiring, a semiconductor layer, a counter substrate provided with a common electrode disposed opposite to the TFT substrate at a predetermined interval, and a TFT substrate, The liquid crystal layer is filled between the counter substrate and the liquid crystal layer.

  As the wiring material such as the source-drain wiring, pure Al or Al alloy such as Al—Nd is widely used because of its low electrical resistivity and easy microfabrication.

  The applicant of the present application also has a low contact resistance even if the TFT substrate is directly connected to the transparent conductive film (for example, ITO film) constituting the transparent pixel electrode without passing through the barrier metal layer (hereinafter, such characteristics are exhibited). It has been proposed that an Al alloy film (sometimes referred to as “DC property”) may be applied to the wiring (for example, Patent Document 1).

  Conventionally, the manufacture of the liquid crystal display panel as shown in FIG. 1 of the above-mentioned Patent Document 1 has been performed consistently in the same factory. The number of cases where a transparent conductive film (for example, ITO film) as shown in FIG. 2 is formed in one factory and the subsequent processes are performed in another factory is increasing. In such a case, water vapor permeates from a pinhole (discontinuous portion of the transparent conductive film, hereinafter sometimes referred to simply as “pinhole”) existing in the transparent conductive film during transportation and storage to another factory. Corrosion (hereinafter sometimes referred to as “pinhole corrosion”) occurs between the transparent conductive film (ITO film) and the Al alloy film constituting the source-drain wiring, and may be recognized as a black spot. . When the black spots occur, it becomes difficult to manufacture a highly reliable display device.

  In order to solve such problems, several methods for preventing the corrosion have been proposed. For example, Patent Document 2 discloses that a paint containing a film forming agent and an ion exchange material is applied to the surface of an oxide semiconductor (for example, ITO) constituting a transparent conductive film of a display device. Patent Document 3 discloses that a paint having a water repellent function is applied to the surface of the oxide semiconductor. In these patent documents 2 and 3, corrosion by water vapor | steam is prevented by apply | coating the said coating material to the oxide semiconductor surface.

JP 2009-105424 A Japanese Patent Laid-Open No. 11-286628 Japanese Patent Laid-Open No. 11-323205

  However, when the techniques of Patent Documents 2 and 3 are applied, a process for applying the paint to the surface of the oxide semiconductor (transparent conductive film) is necessary before transportation, and the following process is performed at another factory after transportation and storage. In proceeding, it is necessary to peel off the film / coating formed by the application, and there is a problem that the production efficiency is lowered.

  The present invention has been made paying attention to the above-described circumstances, and an object of the present invention is a display device having a structure in which a transparent conductive film and an Al alloy film are directly connected in a thin film transistor. It is an object of the present invention to provide a display device capable of preventing pinhole corrosion without providing a process such as application and peeling of the corrosion-preventing paint in the manufacturing process.

The display device of the present invention capable of solving the above problems is a display device having a structure in which a transparent conductive film and an Al alloy film are directly connected in a thin film transistor, wherein the Al alloy film is
Ni and / or Co (hereinafter referred to as X element) 0.15 atomic% or less (excluding 0 atomic%) (inclusive of only one species, total amount when including Ni and Co) The same shall apply hereinafter),
Ge is 0.2 atomic% or more and 2.0 atomic% or less, and at least one element selected from the group consisting of La, Gd, Nd and Y (hereinafter referred to as Z element) is 0.05 atomic% or more and 1 0.0 atomic% or less (when only one type is included, it is a single amount, and when two or more types are included, it is the total amount; the same shall apply hereinafter), and
It is characterized in that the aspect ratio (corrosion depth / corrosion diameter) of corrosion holes observed on the surface of the Al alloy film is 0.12 or less.

In a preferred embodiment, the Ge and Z element contents of the Al alloy film satisfy the following formula (1).
Ge / Z ≦ 10 (1)

  In a preferred embodiment, the content of the smaller one of Ge and Z elements in the Al alloy film is 1.5 times or more the content of the X element in the Al alloy film.

  According to the present invention, an Al alloy film in a display device can be directly connected to a transparent pixel electrode (transparent conductive film), and a transparent conductive film such as an ITO film can be formed on the Al alloy film without generating a pinhole. Can be formed. As a result, pinhole corrosion can be suppressed without providing a process such as application or peeling of the anticorrosion coating as in the prior art. Therefore, a high-performance display device can be manufactured with low cost and high productivity.

FIG. 1 is a schematic cross-sectional view illustrating that pinholes (ITO discontinuities) are formed when the aspect ratio of corrosion holes on the surface of the Al alloy film is large. FIG. 2 is a schematic cross-sectional view illustrating that the formation of pinholes (ITO discontinuities) is suppressed when the aspect ratio of the corrosion holes on the Al alloy film surface is small. FIG. 3 is a view showing a planar TEM observation photograph taken in Example, and an EDX analysis result and a nano-diffraction analysis result of precipitates (Nos. 1 and 2) in the photograph. 4 is a diagram showing the nano-diffracting pattern and detailed analysis results of the precipitate (No. 2) in FIG.

  The present inventors have assumed that the contact resistance can be sufficiently reduced (with excellent DC properties) even when the barrier metal layer is omitted and the transparent pixel electrode (transparent conductive film) is directly connected. In order to realize a display device with reduced pinhole corrosion (spots) even in the environment, we conducted intensive research. Hereinafter, the present invention will be described in detail together with the background.

  As described above, when the transparent electrode film is an ITO film, for example, when the transparent electrode film is an ITO film, moisture penetrates from the pinhole formed in the ITO film, and moisture reaches the interface between the ITO film and the Al alloy film. The cause is thought to cause galvanic corrosion.

  Therefore, as a result of investigating the cause of the occurrence of the pinhole, the present inventors have found that a rough corrosion hole is formed on the surface of the Al alloy film at the black spot (pinhole corrosion) portion. We paid attention to what seems to be the cause of the occurrence, that is, the state of the surface of the Al alloy film that forms the foundation of the ITO film formation. Further, when the relationship between the shape of the corrosion holes and the occurrence of pinholes was examined, the aspect ratio (corrosion depth / corrosion diameter) of the corrosion holes formed by cleaning with the resist stripping solution in the manufacturing process of the display device was It was found to be related to the generation of holes.

  1 and 2 are schematic cross-sectional views illustrating that the aspect ratio of corrosion holes formed on the surface of an Al alloy film affects the presence or absence of pinholes when an ITO film is formed on the Al alloy film. is there.

  As shown in FIG. 1, when the aspect ratio of the corrosion hole is large (FIG. 1A), when the ITO film is formed, a discontinuous portion (pinhole) is generated in the ITO film (FIG. 1B). On the other hand, when the aspect ratio of the corrosion holes is small as shown in FIG. 2 (FIG. 2A), the ITO film can be formed almost continuously when the ITO film is formed (FIG. 2B). ). In other words, the formation of pinholes is affected by the surface state (specifically, the corrosion state) of the Al alloy film, and in order to prevent the occurrence of pinholes, the aspect ratio of the corrosion holes existing on the surface of the Al alloy film is reduced. It is considered necessary.

  Therefore, when the aspect ratio of the corrosion hole is reduced to further reduce whether the pinhole is easily formed, if the aspect ratio of the corrosion hole is 0.12 or less, the pinhole is hardly formed. It was found that the generation of sunspots can be prevented in a humid environment. The aspect ratio is preferably 0.1 or less.

  In addition, the corrosion hole said by this invention means the corrosion hole which has a corrosion diameter of 100 nm or more recognized in an AFM (atomic force microscope) apparatus. The aspect ratio is obtained by the method shown in the examples described later.

  By the way, the Al alloy film which becomes the foundation of the ITO film formation generally undergoes the following steps. That is, after the Al alloy film is formed, an insulating film is formed on the Al alloy film, and precipitates are formed in the Al matrix due to the thermal history in the film forming process of the insulating film. Next, in the pattern formation process of the insulating film by photolithography, the photoresist on the insulating film is removed (cleaning liquid cleaning) using a resist stripping solution containing amines (hereinafter simply referred to as “stripping solution”). However, in this step, galvanic corrosion occurs due to the large potential difference between the precipitate and the Al matrix, and electrochemically base Al is ionized and eluted, forming corrosion holes around the precipitate. (See FIG. 1 (a) and FIG. 2 (a)).

Therefore, the present inventors further examined a means for making the corrosion holes have the shape (aspect ratio: 0.12 or less) in consideration of the components of the Al alloy film and the history of the manufacturing process.
(1) Since the size of the corrosion holes formed around the precipitate depends on the size of the precipitate, it is necessary to control the precipitate form of the Al alloy film used for cleaning the stripping solution. (1-1) It is necessary to define the component composition of the Al alloy film, and (1-2) the heating condition of the Al alloy film is performed under the recommended conditions, and (2) the stripping solution is cleaned. We found that it was necessary to carry out under the recommended conditions, and examined each means in more detail. Hereinafter, each means will be described in detail.

(1) Precipitate control of Al alloy film used for stripping solution cleaning In order to ensure the DC properties of the Al alloy film and the ITO film, it is necessary to remove the surface oxide film of the Al alloy film in the stripping solution cleaning step. For this purpose, it is necessary to cause corrosion on the surface of the Al alloy film. In the state where no precipitate is present, the corrosion does not proceed and the surface oxide film cannot be removed. Therefore, it is necessary to cause the Al alloy film surface to corrode to some extent by the presence of the precipitate.

However, when the precipitate is, for example, Al ₃ Ni or Al ₉ Co ₂ , corrosion holes having a high corrosion rate and a large aspect ratio are formed. On the other hand, when a Ge- (rare earth element) intermetallic compound such as GeNd is deposited as a precipitate, the corrosion rate is too slow, and the oxide film is removed in the usual stripping solution cleaning step. Corrosion as much as possible does not occur.

In view of the above circumstances,
(A) A viewpoint of sufficiently removing the oxide film in a usual stripping solution cleaning step for securing DC properties; and (b) Corrosion holes having a small aspect ratio (corrosion with an aspect ratio of 0.12 or less). From the viewpoint of forming (holes), the preferred embodiment of the precipitate was examined. In the present invention, Ge and one or more elements (Z element) selected from the group consisting of La, Gd, Nd, and Y were used. X-containing intermetallic compound (Ge-Z) contains a trace amount of X element (it is considered that X element is dissolved in Ge-Z intermetallic compound). We have found that it is sufficient to deposit Z).

This X-containing Ge-Z contains a trace amount of X element (Ni and / or Co), so that the corrosion rate is slower than that of Al ₃ Ni and Al ₉ Co ₂ , and a Ge—Z intermetallic compound (for example, GeNd). It is thought that it can be earlier. As a result, it is considered that the oxide film can be removed by causing sufficient corrosion, and the DC property can be ensured, and the formation of the Al ₃ Ni and the like can be suppressed and a corrosion hole having a small aspect ratio can be formed. In the present invention, the X-containing Ge-Z does not become a coarse precipitate that causes a problem, and therefore the size is not particularly limited.

  Next, (1-1) the composition of the Al alloy film for positively precipitating the X-containing Ge—Z while ensuring excellent DC properties, etc., and (1-2) the formation of the Al alloy film The subsequent heating conditions will be described in detail.

(1-1) Component composition of Al alloy film The Al alloy film according to the present invention first contains Ni and / or Co (X element) in an amount of 0.15 atomic% or less (not including 0 atomic%). Ni and Co are elements that improve DC properties with the ITO film. From such a viewpoint, it is preferable to contain 0.02 atomic% or more of the X element. More preferably, it is 0.04 atomic% or more. However, these elements are also elements for forming Al ₃ Ni, Al ₉ Co _{2 and the} like that cause crater corrosion having a large aspect ratio in the stripping solution cleaning step. If these elements are contained excessively, it becomes difficult to suppress precipitates, so the content of the X element is set to 0.15 atomic% or less. Preferably it is 0.12 atomic% or less.

  Moreover, the Al alloy film according to the present invention further contains Ge in a range of 0.2 atomic% to 2.0 atomic%. Since this Ge is also an element necessary for ensuring excellent DC properties, it is contained in an amount of 0.2 atomic% or more. Preferably it is 0.4 atomic% or more. Ge is an element that also contributes to the formation of the X-containing Ge—Z.

  On the other hand, if the amount of Ge is excessive, the electrical resistivity is increased, so the content is made 2.0 atomic% or less. Preferably it is 1 atomic% or less.

  The Al alloy film according to the present invention further contains 0.05 atomic% or more and 1.0 atomic% or less of one or more elements (Z element) selected from the group consisting of La, Gd, Nd, and Y.

La, Gd, Nd, and Y are elements that combine with Ge to form the X-containing Ge—Z. That is, when Ni and Co are used for forming coarse precipitates such as Al ₃ Ni and Al ₉ Co ₂ by being contained at the same time as Ge, X-containing Ge-Z (Ni-containing Ge-Z, Co-containing Ge-Z, etc.) The formation of coarse precipitates such as Al ₃ Ni and Al ₉ Co ₂ can be suppressed. In order to exhibit such an effect, the Z element is contained in an amount of 0.05 atomic% or more (preferably 0.1 atomic% or more). On the other hand, from the viewpoint of reducing electrical resistivity after heat treatment, the amount of Z element is set to 1.0 atomic% or less (preferably 0.7 atomic% or less). Among the above Z elements, Nd, La, and Y are preferable, and it is particularly preferable that Nd is contained in an amount of 0.2 atomic% to 0.5 atomic% as the Z element.

  Examples of the Al alloy film according to the present invention include those that satisfy the above-mentioned components and the balance is made of Al and inevitable impurities.

Moreover, it is preferable that content of the said Ge and Z element satisfy | fills following formula (1) further.
Ge / Z ≦ 10 (1)

As described above, X-containing Ge—Z can be formed as a precipitate in the Al alloy film by containing Ge and Z elements simultaneously. The atomic ratio of Ge and Z in X-containing Ge—Z is approximately 1: 1. Therefore, when the amount of Ge is extremely small relative to the amount of Z element, the formation of X-containing Ge—Z is not sufficient, and Al ₃ Ni, Al ₉ Co _2, etc. are likely to be formed. Therefore, in the present invention, the Ge / Z ratio is preferably set to 0.3 or more. More preferably, it is 2.0 or more. On the other hand, even if the amount of Ge is excessive relative to the amount of Z element, the amount of X-containing Ge—Z formed is saturated and the electrical resistivity after the heat treatment tends to be high. Therefore, the Ge / Z ratio is preferably 10 or less. More preferably, it is 5 or less.

  Further, in the present invention, the content of the smaller one of Ge and Z elements in the Al alloy film is the content of the X element in the Al alloy film (a single amount when only one kind is included, Ni And when Co is included, the total amount is preferably 1.5 times or more.

In the present invention, the X element is precipitated not as Al ₃ Ni or Al ₉ Co ₂ but as X-containing Ge—Z, but the Ge constituting the X-containing Ge—Z with respect to the amount of X element in the Al alloy film. When the amount of the -Z intermetallic compound is small, the X element becomes excessive and the Al ₃ Ni and the like are likely to precipitate. Therefore, in order to positively form X-containing Ge-Z in the presence of a sufficient amount of Ge-Z intermetallic compound relative to the amount of X element in the Al alloy film, It is preferable that the content of whichever is smaller is 1.5 times or more (more preferably 2 times or more) the content of the X element.

(1-2) Heating conditions for Al alloy film In the present invention, in order to positively precipitate X-containing Ge—Z while suppressing the precipitation of Al ₃ Ni and the like, further to the ultimate temperature in the heat treatment of the Al alloy film It is preferable that the rate of temperature rise is 5 ° C./min or less. More preferably, it is 1 ° C./min or less. In the component system defined in the present invention, for example, Ni-containing Ge—Z precipitates at about 250 ° C. in the heat treatment process, whereas, for example, Al ₃ Ni precipitates at about 290 to 300 ° C. Therefore, in the present invention, in order to suppress the formation of Al ₃ Ni, it is effective that the reached temperature is lower than 290 ° C.

  The heating of the Al alloy film is performed so that the heat history after the formation of the Al alloy film (for example, the step of forming an insulating film (for example, a SiN film) formed after the formation of the Al alloy film) satisfies the above temperature and time. In addition, a heat treatment step for the purpose of precipitation may be provided.

(2) Stripping solution cleaning conditions After an insulating film is formed on the Al alloy film, a pattern is formed on the insulating film by a photolithography method. In this process, the photoresist on the insulating film is generally removed using a stripping solution containing amines. However, when water is mixed in the stripping solution, it shows alkalinity. When exposed for a long time, corrosion of the Al alloy film proceeds excessively, and even if X-containing Ge—Z is deposited as the precipitate, corrosion holes having a large aspect ratio are likely to be formed. Therefore, in order to make the corrosion hole into a desired shape, it is preferable to shorten the stripping solution immersion time in this step, and it is preferable to set it to 2 minutes or less. More preferably, it is 1.5 minutes or less. In addition, it is preferable that it is 1 minute or more from a viewpoint of fully wash | cleaning stripping solution.

  In addition, since the corrosion rate is affected by the temperature and pH of the solution to be immersed, immediately after immersion in the stripping solution, the corrosion rate is set to low temperature (preferably 20 ° C. or less) and neutral (pH 6 to 8) (for example, examples described later). It is preferable to wash with pure water at the above temperature).

  In manufacturing the display device of the present invention, the component composition of the Al alloy film should be as specified, and the heating conditions (heat treatment / heat history conditions) and the conditions in the stripping solution cleaning process should be the recommended conditions described above. Other than the above, there is no particular limitation, and a general process of the display device (for example, the manufacturing process described in Patent Document 1) may be adopted.

  The Al alloy film according to the present invention is preferably used for a source electrode and / or a drain electrode and a signal line in a TFT substrate of a display device. In particular, when the Al alloy film is applied to the drain electrode that is directly connected to the transparent conductive film, the effects of the present invention are sufficiently exhibited. The Al alloy film according to the present invention can also be used as a gate electrode and a scanning line. In this case, all of the Al alloy wirings on the TFT substrate can have the same component composition.

  In the present invention, the requirements constituting the TFT substrate and the display device other than the Al alloy film in the display device are not particularly limited as long as they are normally used. Examples of the transparent pixel electrode (transparent conductive film) used in the present invention include an indium tin oxide (ITO) film and an indium zinc oxide (IZO) film.

  EXAMPLES Hereinafter, the present invention will be described more specifically with reference to examples. However, the present invention is not limited by the following examples, but may be appropriately modified within a range that can meet the purpose described above and below. Of course, it is possible to implement them, and they are all included in the technical scope of the present invention.

  Al alloy films (thickness = 300 nm) having various alloy compositions shown in Table 1 were obtained by DC magnetron sputtering method (conditions: substrate = glass substrate (Eagle 2000 manufactured by Corning), atmosphere gas = argon, pressure = 2 mTorr, substrate) The film was formed at a temperature = 100 ° C.

  The content of each alloy element in the various Al alloy films was determined by an ICP emission analysis (inductively coupled plasma emission analysis) method.

  And the heat history received by film-forming of the insulating film (SiN film) on Al alloy film was simulated, and the heat processing hold | maintained at 320 degreeC for 30 minutes was performed. Note that the rate of temperature increase up to 320 ° C. was 3 ° C./min.

  Precipitates present in the Al alloy films (No. 1 and No. 2 Al alloy films in Table 1) after the heat treatment and before cleaning with the stripping liquid described below are removed by TEM-HAADF (High Angle Dark Field Method). (Resolution: 1 nm), two precipitates (1 and 2 in FIG. 3) were subjected to EDX analysis, and among these, precipitate 2 was subjected to nano-diffraction analysis. The results are shown in FIGS.

  3 and 4 that the Al alloy film of the present invention has Ni-containing Ge—Nd having a Ge—Nd crystal structure and containing Ni as precipitates.

<Peeling liquid cleaning>
Next, the removal of the photoresist during the pattern formation of the insulating film was simulated, and the following stripping solution cleaning was performed on the Al alloy film after the heat treatment. That is, using an amine resist stripping solution “TOK106” manufactured by Tokyo Ohka Kogyo Co., Ltd., and immersed in an aqueous solution (liquid temperature: about 25 ° C.) adjusted to pH = 10.5 for 1 minute, then adjusted to pH = 9.5. The sample was immersed in the adjusted aqueous solution (liquid temperature: about 25 ° C.) for 3 minutes, then washed with pure water (liquid temperature: about 25 ° C.) and then dried to obtain a sample. In Table 1, No. For No. 14, the stripper solution was washed in the same manner as above except that the immersion time of the aqueous solution (liquid temperature: about 25 ° C.) adjusted to pH = 9.5 was set to 20 minutes.

<Aspect ratio evaluation of corrosion holes>
Using an atomic force microscope (AFM), five visual fields of 20 μm × 20 μm were observed on the surface of the sample, and the corrosion depth and the diameter of each of 10 arbitrary corrosion holes in the visual field were observed. The aspect ratio (corrosion depth / corrosion diameter) was calculated. And the average value of the aspect-ratio of 10 said corrosion holes was calculated | required.

<Pinhole corrosion test>
Next, an ITO film (film thickness 60 nm) was formed on the sample surface after the stripping solution was washed under the following conditions. That is, using a 4-inch ITO target, an ITO film was formed by a DC magnetron sputtering method (conditions: substrate temperature: room temperature, film forming power: 150 W, atmospheric gas: argon, pressure: 0.8 mTorr). .

Then, a pinhole corrosion test was performed by simulating the transportation and storage conditions as described above and exposed to a humid environment of 60 ° C. × 90% RH for 500 hours. The surface after this test was magnified 1000 times with an optical microscope. (Observation range: about 8600 μm ² ), the number of existing black spots was counted, the number per 100 μm ² was calculated, and the black spot density (ITO pinhole density) after the test was obtained.

And when the said black spot density is 0.15 piece / 100 micrometer < ² > or less, it evaluates that the pinhole generation | occurrence | production of ITO film | membrane is suppressed and pinhole corrosion is fully suppressed ((circle)), The said black spot density Is more than 0.15 / 100 μm ² , it was evaluated that many pinholes were generated in the ITO film and pinhole corrosion was generated in the corrosion test (×).

  These results are shown in Table 1.

  From Table 1, it can be considered as follows.

That is, no. 1 to 10 satisfy the requirements stipulated in the present invention, so that the formation of coarse precipitates such as Al ₃ Ni is suppressed, and the aspect ratio of the corrosion holes can be made 0.12 or less. It is thought that they are formed almost continuously. As a result, the occurrence of black spots (pinhole corrosion) due to the corrosion test is sufficiently suppressed.

In contrast, no. No. 11, the total amount of Ni and Co is excessive, and formation of Al ₃ Ni and Al ₉ Co ₂ cannot be suppressed. As a result, corrosion holes with a large aspect ratio are generated in the stripping solution cleaning step, A lot of pinhole corrosion occurred.

No. Since 12 and 13 do not contain Ge (No. 13 has an excessive Ni amount), Ni-containing Ge—Z was not formed, and formation of Al ₃ Ni could not be suppressed. As a result, corrosion holes with a large aspect ratio were generated, and many black spots (pinhole corrosion) were generated.

  These No. In Nos. 11 to 13, crater corrosion of precipitate bases occurred in the stripping solution cleaning process, and it was recognized as a black spot even after the ITO film was laminated, and became more noticeable by wet exposure.

  No. No. 14, the component composition of the Al alloy film satisfies the regulations, but the stripping solution cleaning process takes a long time, so that corrosion holes with a large aspect ratio are generated, resulting in black spots (pinhole corrosion). occured.

  No. No. 15 is an example in which the ratio of Ge to Ni (Ge / Ni) does not satisfy the preferred range of the present invention (1.5 times or more), and many black spots (pinhole corrosion) occurred.

Claims (3)

A display device having a structure in which a transparent conductive film and an Al alloy film are directly connected in a thin film transistor, wherein the Al alloy film is
Ni and / or Co (hereinafter referred to as X element) 0.15 atomic% or less (excluding 0 atomic%),
Ge is 0.2 atomic% or more and 2.0 atomic% or less, and at least one element selected from the group consisting of La, Gd, Nd and Y (hereinafter referred to as Z element) is 0.05 atomic% or more and 1 0.0 atomic% or less, and
An aspect ratio (corrosion depth / corrosion diameter) of corrosion holes observed on the surface of the Al alloy film is 0.12 or less. The display device according to claim 1, wherein contents of Ge and Z elements in the Al alloy film satisfy the following formula (1).
Ge / Z ≦ 10 (1)   3. The display device according to claim 1, wherein a content of the smaller one of Ge and Z elements in the Al alloy film is 1.5 times or more of a content of X element in the Al alloy film.