JP2011017944A - Aluminum alloy film for display device, display device, and aluminum alloy sputtering target - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an Al alloy film for a display device, the alloy film showing low contact resistance even when the film is directly connected to a transparent pixel electrode eliminating a barrier metal layer, and higher corrosion resistance against a developing solution or corrosion resistance against a peeling solution in a manufacturing process of the display device.SOLUTION: The Al alloy film is directly connected to a transparent conductive film on a substrate of the display device. The Al alloy film contains: 0.5 atomic% or less (but not 0 atomic%) of Ni and/or Co element belonging to a group A; 0.2 to 2.0 atomic% of Ge; and 3 atomic% or less (but not 0 atomic%) of Y and/or Zr element belonging to a group B.

Description

  The present invention relates to an Al alloy film for a display device, a display device, and an Al alloy sputtering target, and in particular, corrosion resistance in stripping solution cleaning (hereinafter sometimes referred to as stripping solution corrosion resistance), developer corrosion resistance, and heat resistance. The present invention relates to an Al alloy film having excellent properties, a display device using the Al alloy film for a thin film transistor, and an Al alloy sputtering target useful for forming the Al alloy film.

  Liquid crystal display devices (LCD: Liquid Crystal Display) are used for small and medium-sized devices such as displays for mobile phones and mobile terminals, PC monitors, etc., and in recent years, they are also used for large-sized TVs and the like due to their increasing size. . Liquid crystal display devices are divided into a simple matrix type and an active matrix type, a thin film transistor (TFT) substrate and a counter substrate, a liquid crystal layer injected between them, a resin film such as a color filter and a polarizing plate, a back surface. Consists of lights and the like. On the TFT substrate, switching elements and pixels, and further scanning lines and signal lines for transmitting electric signals to the pixels are formed by making full use of fine processing technology cultivated in semiconductors.

  For wiring materials used for the scanning lines and signal lines, pure Al or Al alloys such as Al—Nd are widely used because of their low electrical resistivity and easy microfabrication. A barrier metal layer made of a refractory metal such as Mo, Cr, Ti, or W is usually provided between the wiring made of pure Al or Al alloy and the transparent pixel electrode. The reason why the barrier metal layer is formed in this manner is to ensure heat resistance and electrical conductivity when a wiring made of pure Al or Al alloy is directly connected to the transparent pixel electrode.

  However, in order to form a barrier metal layer, an apparatus having a film forming chamber necessary for forming the wiring must be additionally equipped with a film forming chamber for forming a barrier metal layer. As cost reduction associated with mass production of liquid crystal display devices progresses, it is not possible to neglect the increase in manufacturing cost and the decrease in productivity due to the formation of the barrier metal layer.

  Therefore, a direct contact technique that can eliminate the formation of the barrier metal layer has been proposed. For example, in Patent Documents 1 and 2, even if the formation of the barrier metal layer is omitted and the Al alloy wiring is directly connected to the transparent pixel electrode, the contact resistance is low (hereinafter, such characteristics are referred to as “low contact resistance”). There is a proposal for a direct contact technique in which the electrical resistivity of the Al alloy wiring itself is small and the heat resistance is also excellent. Specifically, it is described that by adding a predetermined amount of elements such as Ni, Ag, Zn, and Co, the contact resistance with the transparent pixel electrode can be lowered and the electrical resistivity of the wiring itself can be kept low. Yes. It also describes that heat resistance can be improved by adding rare earth elements such as La, Nd, Gd, and Dy. Further, in Patent Document 3, if a wiring material of a display device having a structure directly connected to a transparent pixel electrode layer or a semiconductor layer is used, an Al—Ni alloy containing a predetermined amount of B is used for direct connection. It is stated that there is no increase in contact resistance or poor connection.

JP 2004-214606 A JP 2006-261636 A JP 2007-186777 A

  By the way, when the barrier metal layer is omitted as shown in the above cited documents 1 to 3, the Al alloy film has excellent contact resistance (low contact resistance) with the transparent pixel electrode and low electrical resistivity, as well as better corrosion resistance. It is required to have both. In particular, the TFT substrate manufacturing process passes through a plurality of wet processes. However, if a metal nobler than Al is contained as an alloy element, a problem of galvanic corrosion appears and the corrosion resistance deteriorates.

  For example, in a cleaning process for removing a photoresist (resin) formed in a photolithography process, water washing is continuously performed using an organic stripping solution containing amines. However, when amines and water are mixed, an alkaline solution is formed, which causes a problem that Al is corroded in a short time. By the way, the Al alloy film has received a thermal history before the peeling cleaning step, and an Al-based precipitate containing an alloy element is formed in the Al matrix in the course of the thermal history. Since the potential difference between the Al-based precipitate and the Al matrix is large, the galvanic corrosion occurs at the moment when the amines, which are components of the organic stripping solution, come into contact with water in the stripping cleaning process. There is a problem that Al ionizes and elutes to form pit-like pitting corrosion (hereinafter sometimes referred to as “black spots”). When black spots occur, the transparent pixel electrode (ITO film) becomes discontinuous and may be recognized as a defect in appearance inspection, which may lead to a decrease in yield.

  In the photolithography process, an alkaline developer containing, for example, TMAH (tetramethylammonium hydroxide) is used. However, in the case of a direct contact structure, the barrier metal layer is omitted, so the Al alloy film is exposed, and development is performed. The etching rate (dissolution rate) of the Al alloy film in the liquid process is remarkably increased, and is easily damaged by the developer (thinning of the Al alloy film). It is known that the etching of the Al alloy film in the development process is accelerated by galvanic corrosion accompanying the concentration of the additive element, particularly when an element that is electrochemically noble than Al such as Ni or Co is added. This tendency appears remarkably. When the etching rate in the development process is increased, problems such as difficulty in reworking the wiring and a decrease in manufacturing yield occur.

  Of the above Patent Documents 1 to 3, Patent Documents 1 and 3 have not been sufficiently studied by paying attention to the corrosion resistance of the Al alloy film. Patent Document 2 describes that the corrosion resistance against an alkaline developer can be improved, but it has not been studied until the corrosion resistance is sufficiently enhanced, including the corrosion resistance against an organic stripping solution.

  The present invention has been made paying attention to the above circumstances, and its object is to exhibit a low contact resistance even when the barrier metal layer is omitted and to be directly connected to a transparent pixel electrode, and to produce a display device. An object of the present invention is to provide an Al alloy film for a display device and a display device which have improved developer corrosion resistance and stripping solution corrosion resistance in the process.

  The Al alloy film for a display device excellent in peeling solution corrosion resistance and developer corrosion resistance according to the present invention that can achieve the above object is an Al alloy film directly connected to a transparent conductive film on a substrate of the display device. The Al alloy film has a Ni and / or Co element belonging to group A of 0.5 atomic% or less (excluding 0 atomic%), Ge of 0.2 to 2.0 atomic%, It has a gist in that the element of Y and / or Zr belonging to B contains 3 atomic% or less (excluding 0 atomic%).

  In a preferred embodiment, the Al alloy film for a display device includes Ni as an element belonging to the group A of 0.5 atomic% or less (not including 0 atomic%), and Ge of 0.2 to 2.0 atoms. %, And Y as an element belonging to the group B contains 1 to 3 atomic%.

  In a preferred embodiment, the Al alloy film for a display device has a ratio (β / α) of the content (β) of the element belonging to the group B to the content (α) of the element belonging to the group A is 0. Satisfies 5 or more and 7 or less.

  In a preferred embodiment, the Al alloy film for a display device has a ratio (β / α) of the content (β) of the element belonging to the group B to the content (α) of the element belonging to the group A is more than 7. Satisfied.

In a preferred embodiment, the Al alloy film for display device has a circle-equivalent diameter (hereinafter, may be referred to as “particle size”) of the precipitate after the heat treatment exceeds 100 nm, and is composed of only Al and Ni. The number of precipitates (typically Al ₃ Ni) and / or precipitates composed only of Al and Co (typically Al ₉ Co ₂ ) is suppressed to 4.0 or less per 100 μm ^2. It is what.

  In a preferred embodiment, the Al alloy film for display device further contains at least one selected from the group consisting of La, Nd, and Gd in an amount of 0.5 atomic% or less (excluding 0 atomic%).

  The display device of the present invention is one in which the Al alloy film for display device described above is used for a thin film transistor.

  The present invention also includes within the scope of the present invention an Al alloy sputtering target used for forming an Al alloy film that is directly connected to the transparent conductive film on the substrate of the display device. Here, the Al alloy includes Ni and / or Co elements belonging to Group A of 0.5 atomic% or less (excluding 0 atomic%), Ge of 0.2 to 2.0 atomic%, It has a gist in that it contains 3 atomic% or less (not including 0 atomic%) of Y and / or Zr elements belonging to Group B, and the balance is Al and inevitable impurities.

  In a preferred embodiment, the Al alloy includes Ni as an element belonging to the group A of 0.5 atomic% or less (not including 0 atomic%), Ge of 0.2 to 2.0 atomic%, It contains 1 to 3 atomic% of Y as an element belonging to group B, and the balance is Al and inevitable impurities.

  In a preferred embodiment, the Al alloy further contains 0.5 atomic% or less (excluding 0 atomic%) of at least one selected from the group consisting of La, Nd, and Gd.

  According to the present invention, an Al alloy film can be directly connected to a transparent pixel electrode (transparent conductive film, oxide conductive film) without interposing a barrier metal layer, and is excellent in alkali developer corrosion resistance and stripping solution corrosion resistance. An Al alloy film for a display device can be provided. Therefore, if the Al alloy film of the present invention is applied to a display device, discontinuity of the ITO film generated in the manufacturing process of the TFT substrate can be suppressed, and a highly reliable display device can be provided.

FIG. 1A shows the No. of the example. 15 is a diagram showing a planar TEM photograph and an EDX analysis result of 15 (example of Y added as an element of group B), and FIG. It is a figure which shows the planar TEM photograph and EDX analysis result of 18 (Zr addition example as an element of group B). FIG. It is a figure which shows the planar TEM photograph and EDX analysis result of 22 (element B additive-free). FIG. 3 is a graph showing the relationship between the amount of Y in the Al alloy film used in the examples and the black spot density. FIG. 4 is a graph showing the relationship between the amount of Zr in the Al alloy film used in the example and the black spot density. FIG. 5 is a diagram showing a Kelvin pattern (TEG pattern) used for measuring the contact resistance between the Al alloy film and the transparent pixel electrode.

The present inventors can sufficiently reduce the contact resistance when directly connected to the transparent pixel electrode even if the barrier metal layer is omitted, and further, the developer corrosion resistance and the peeling in the manufacturing process of the display device. In order to provide an Al alloy film excellent in liquid corrosion resistance (hereinafter, sometimes represented by chemical corrosion resistance), studies have been made. Particularly, in the present invention, Al- (Ni and / or Co) -Ge containing Ni and / or Co excellent in performance of reducing contact resistance with a transparent conductive film and Ge contributing to reduction of contact resistance as well. In order to further promote the corrosion resistance of the alloy film, investigations have been made focusing on coarse Al-based precipitates that serve as a base point of corrosion (black spots) in the peeling cleaning process. As a result, if a predetermined amount of Y and / or Zr element is added to the Al- (Ni and / or Co) -Ge alloy film, only coarse Al and Ni / Co having a particle diameter of more than 100 nm are included. The number of precipitates (typically Al ₃ Ni and / or Al ₉ Co ₂ precipitates and main causative substances of corrosion) is reduced, and the precipitates further contain the above Y and Zr. As the number of fine Al-based composite precipitates (substances useful for reducing corrosion) increases, it is found that the black spots generated around the composite precipitates are refined to a size that cannot be visually recognized, and the stripping solution corrosion resistance is improved. Completed the invention.

Specifically, regarding the precipitates represented by the above Al ₃ Ni and / or Al ₉ Co ₂ , the particle size of each precipitate (equivalent circle diameter calculated by image analysis of the area of the precipitate) was observed. Sometimes, preferably, the above-mentioned precipitates having a particle size exceeding 100 nm satisfying 4.0 or less per 100 μm ² have a reduced black spot density and improved stripping solution corrosion resistance. . The smaller the number of precipitates per 100 μm ² (precipitate density), the better, and 1.0 or less is more preferable. Strictly speaking, the preferred number of precipitates varies depending on the composition of the precipitates, and when the precipitates are composed only of Al and Ni represented by Al ₃ Ni, 4.0 or less per 100 μm ² is preferable. In the case of consisting only of Al and Co represented by Al ₉ Co ₂ , 1.0 or less per 100 μm ² is preferable.

The detailed reason why the chemical corrosion resistance is improved by the present invention is unknown, but by using an Al alloy film having the above composition containing Y or Zr, such as Al ₃ Ni and Al ₉ Co ₂ (compared to Al). It is not an electrochemically noble precipitate, but is electrochemically low such as Al—Ni—Y, Al—Ni—Zr, Al—Co—Y, and Al—Ni—Zr in which Y and Zr are further bonded to these. Since composite precipitates are generated, the potential difference from the Al matrix is reduced, and galvanic corrosion in the stripping solution cleaning process is suppressed, and the corrosion rate is considered to be slow.

Here, the composite precipitate useful for improving the corrosion resistance of the stripping solution needs to contain at least both the group A element (Ni / Co) and the group B element (Y / Zr). That is, Ni / Co in precipitates such as Al ₃ Ni and Al ₉ Co ₂ that cause corrosion is consumed in a composite precipitate of Al— (Ni / Co) — (Y / Zr), resulting in a result. Further, the number of precipitates of Al ₃ Ni and Al ₉ Co ₂ is reduced, and the corrosion resistance of the stripping solution is improved. The composite precipitate may further contain a rare earth element described later. From the above definition, a precipitate not containing an element of group A (for example, an Al—Ge—Y—La precipitate such as symbol 3 in FIG. 1A described later) does not become a starting point of corrosion. It is not included in the composite precipitate.

On the other hand, precipitates represented by “Al ₃ Ni and Al ₉ Co ₂ ” [consisting of only Al and group A (Ni / Co) and not containing other elements such as group B elements and rare earth elements] ] Are simply referred to as “precipitates” and are distinguished from the above composite precipitates.

  According to the present invention, the Y or Zr-containing composite precipitate useful for improving the corrosion resistance of the stripping solution is precipitated. The planar TEM (transmission electron microscope, magnification of 300,000 times) in FIGS. This will be explained with reference to the photos. 1 (a) and 1 (b) are respectively Nos. 1 in Table 1 used in Examples described later. 15 (Al-0.21% Ni-0.34% Ge-1.52% Y-0.18% La) and No. 15 18 (Al-0.19% Ni-0.31% Ge-0.71% Zr-0.12% La) Al alloy film after heat treatment at 320 ° C. for 30 minutes (TEM observation image, magnification) 300,000 times). Below each figure, the results (remainder: Al and inevitable impurities) obtained by analyzing the composition of each precipitate of symbols 1 to 8 by the EDX method are also shown. For reference, FIG. 2 shows No. 1 in Table 1 not containing Y or Zr. 22 shows a TEM photograph and EDX analysis result of 22 (Al-0.20% Ni-0.50% Ge-0.50% La).

First, a planar TEM photograph of FIG. 1A (Y addition example) is referred to. Here, fine precipitates having a particle diameter of 100 nm or less, including Al—Ni—Ge—Y—La precipitates as indicated by symbols 1 and 2 and Al—Ge—Y—La precipitates as indicated by symbols 3 are included. Many things have been observed. Of these, the compositions of symbols 1 and 2 have a Ni: Y ratio of approximately 1: 1, and Ge and La are significantly less than Ni and Y. Is considered to be Al ₄ NiY (a composite precipitate in which Al and Y are further bonded to Al ₃ Ni). A technique for directly measuring the potential of such a composite precipitate in a solution has not been established. However, since Al, as well as Al, is an electrochemically base element compared to Al ₃ Ni, these the above composite precipitates element is compounded in Al ₃ Ni is considered to be electrochemically less noble than the Al ₃ Ni. Further, the precipitate of symbol 3 also contains a lot of electrochemically base Y, and, like the deposits of symbols 1 and 2, is considered to be electrochemically base compared to Al ₃ Ni.

Actually, No. 1 in FIG. No. 15 contains no Y in FIG. As shown in Table 1 of the Examples described later, the precipitates exceeding 100 μm were significantly less than 0.1 / 100 μm ² and the sunspot density was 0.2 / 100 μm ² as compared to 22. This is because, by adding Y, more electrochemically base Y-containing Al-based composite precipitates (Al ₄ NiY, etc.) are formed compared to Al ₃ Ni, and the potential difference from the Al matrix is reduced, thereby suppressing galvanic corrosion. It is thought that it was because it was done.

  No. 1 in FIG. 15 is an example of a Y-added Al alloy, but the tendency similar to that discussed in FIG. 1A is the same as that of FIG. 1B using a Zr-added Al alloy containing Zr instead of Y. . 18 was also seen.

First, the planar TEM photograph of FIG. 1B (Zr addition example) is referred to. Here, many fine composite precipitates having a particle size of 100 nm or less, including the precipitates of Al—Ni—Ge—Zr—La of symbols 4 to 8, are observed. The number is 7/100 μm ² . Although the composite precipitates of the above symbols have different contents of Ni, Ge, Zr, and La, each contains a large amount of electrochemically base Zr compared to Al ₃ Ni. Precipitates are considered to be electrochemically less basic than Al ₃ Ni. Actually, No. 1 in FIG. No. 18 has a markedly low black spot density of 4.4 or less / 100 μm ² .

In contrast, No. containing no Y or Zr. When 22 Al alloy film was used, as shown by symbols 9 and 10 in the planar TEM photograph of FIG. 2, a large number of coarse precipitates having a particle size exceeding 100 nm were observed at 4.3 pieces / 100 μm ² . Actually, no. The black spot density of 22 was as high as 8.6 / 100 μm ² , and the stripping solution corrosivity was lowered (see Table 1). In addition, No. No. 22 does not contain Y or Zr, which is an element for improving the corrosion resistance of the stripping solution, but contains a large amount of La, which is an element for improving the corrosion resistance of the developing solution. is there.

  Hereinafter, each element constituting the Al alloy film of the present invention will be described in detail.

(1) Ni and / or Co element belonging to group A is 0.5 atomic% or less (excluding 0 atomic%).
Ni and Co belonging to Group A are useful elements for reducing contact resistance with the transparent conductive film. That is, if Ni or Co is contained as an alloy component in the Al alloy film, conductive Ni / Co-containing precipitates or Ni / Co-containing concentrates are present at the interface between the Al alloy film and the transparent conductive film even at a low heat treatment temperature. An oxide layer is easily formed, and an Al oxide insulating layer can be prevented from being formed at the interface. As a result, the precipitate or concentration between the Al alloy film and the transparent pixel electrode (for example, ITO) can be prevented. It seems that most of the contact current flows through the layers, and the contact resistance can be kept low.

  In the present invention, Ni and Co belonging to group A may be used alone or in combination. When the content of an element belonging to group A (single amount is a single amount, and when both are included is a total amount) is α (atomic%), α is set to 0 in order to effectively exhibit the above action. It is preferable to set it to 0.05 atomic% or more. More preferable α is 0.08 atomic% or more. However, the above action is saturated even if added excessively, and the corrosion resistance (developing solution corrosion resistance) in the developing process is hindered. Therefore, the upper limit of α is set to 0.5 atomic%. A preferable upper limit of α is 0.3 atomic%.

(2) 0.2 to 2.0 atomic% of Ge
Ge is also an element useful for ensuring low contact resistance, like Ni / Co described above. When Ge is segregated at the crystal grain boundary, most of the contact current flows between the Al alloy film and the transparent pixel electrode (for example, ITO film) through the Ge segregation part, and the contact resistance can be kept low. Seem. Moreover, it is considered that Ge segregates at the grain boundaries, so that it effectively acts on the refinement of Al crystal grains, and as a result, contributes to the refinement of precipitates. In order to sufficiently exhibit such an effect, Ge is contained in an amount of 0.2 atomic% or more (preferably 0.3 atomic% or more). On the other hand, when the amount of Ge is too large, the electrical resistivity of the Al alloy film itself increases. Therefore, the Ge amount is set to 2.0 atomic% or less. Preferably it is 1.0 atomic% or less.

(3) 3 atom% or less of elements of Y and / or Zr belonging to group B (excluding 0 atom%)
Group B elements are useful for improving the stripping solution corrosion resistance and developer corrosion resistance of the Al—Ni / Co alloy film. Specifically, it is considered that the addition of at least one group B element lowers the potential of the precipitate containing the element, reduces the potential difference from the Al matrix, reduces the galvanic corrosion rate, and improves the stripping solution corrosion resistance. It is done. In addition, since the above elements are also concentrated on the surface of the Al alloy film, the dissolution rate of the Al alloy film when exposed to the stripping solution water is reduced to extend the time until the occurrence of corrosion, and the stripping solution has corrosion resistance. It is thought to improve. Furthermore, the above elements have an effect of reducing the amount of corrosion in the development process and contribute to the corrosion resistance of the developer.

  In the present invention, Y and Zr belonging to group B may be used singly or in combination. When the content of the element belonging to Group B (single amount when used alone is the total amount when both are included) is β (atomic%), the above chemical solution corrosion resistance improving effect is effectively exhibited. , Β is preferably 0.05 atomic% or more. More preferable β is 0.2 atomic% or more, and further preferably 0.4 atomic% or more. However, if added excessively, the electrical resistivity of the Al alloy film itself after heat treatment increases, so the upper limit is made 3 atomic%. The electrical resistivity greatly depends on the type and content (total amount) of the additive element, and generally tends to increase as the total amount of the additive element increases. Therefore, in order to realize a low electrical resistivity, β should be as small as possible and is preferably controlled to 1 atomic% or less. Specifically, β may be appropriately determined according to the use of the Al alloy film. For example, when importance is attached to the stripping solution corrosion resistance such as prevention of corrosion inhibition, the content is increased, while the electrical resistivity is reduced. If importance is attached, the content may be controlled as little as possible.

  Strictly speaking, the preferable content of Group B is slightly different depending on the type of element. 3 and 4 show the relationship between the content (β) of group B in the Al alloy film [Al- (Ni / Co) -Ge-La alloy film] used in Examples described later and the black spot density. FIG. 3 is a graph showing the Y amount (atomic%) on the horizontal axis in FIG. 3, and the Zr amount (atomic%) on the horizontal axis in FIG. The smaller the sunspot density, the better the stripping solution corrosion resistance. As is clear from comparison of these figures, generally, Y tends to provide a high black spot density suppressing effect when added in a small amount as compared with Zr.

The effect of suppressing the black spot density due to the addition of Y is remarkably improved when the Y amount is 1 atomic% or more, and the black spot density can be remarkably reduced to 1 or less / 100 μm ² . Moreover, even if a large amount of Y is added in this way, the electrical resistivity is kept low to a level that does not cause a problem in actual operation (see Table 1), and both high corrosion resistance of the stripping solution and low electrical resistivity are achieved. I was able to. The above effect is similarly seen when the amount of Zr is 1 atomic% or more. Therefore, from the viewpoint of suppression of sunspot density, the Y amount and / or Zr amount is preferably controlled to 1 atomic% or more (more preferably 1.5 atomic% or more).

  Effective control according to the application etc. by appropriately controlling the ratio (β / α) of the content (β) of the element belonging to the group B and the content (α) of the element belonging to the group A Can be demonstrated.

  For example, in order to further improve the stripping solution corrosion resistance, the number of elements in group B may be increased as described above, and it is a preferable aspect to control the ratio (β / α) to more than 7. The upper limit can be appropriately determined from the preferred contents of β and α, but is preferably about 10.

  On the other hand, those satisfying the above ratio (β / α) of 0.5 or more and 7 or less are excellent in the balance between electrical resistivity and stripping solution corrosion resistance. In order to further improve the above action, β / α is more preferably 0.8 or more and 3 or less.

  The Al alloy film of the present invention contains the above elements (1) to (3), and the balance is Al and inevitable impurities.

  Furthermore, the Al alloy film of the present invention may contain 0.5 atomic% or less of at least one element selected from a rare earth element group (preferably La, Nd, Gd). The rare earth element is a heat resistance improving element useful for suppressing the generation of hillocks (protruding protrusions) in the heat treatment process and improving the heat resistance of the Al alloy film. It is also an element for improving the corrosion resistance of the developer that contributes to the improvement of the corrosion resistance of the developer by suppressing the etching rate in the developer process. In order to effectively exhibit such an action, it is preferable to contain at least one of the above in a total of 0.1 atomic% or more. However, as the content increases, the electrical resistivity of the Al alloy film itself after heat treatment increases. Therefore, the total amount of rare earth elements (preferably La, Nd, Gd) is preferably 0.5 atomic% or less. More preferably, it is 0.3 atomic% or less.

    The Al alloy film of the present invention has been described above.

  The Al alloy film is desirably formed by a sputtering method using a sputtering target (hereinafter also referred to as “target”). This is because a thin film having excellent in-plane uniformity of components and film thickness can be easily formed as compared with a thin film formed by ion plating, electron beam vapor deposition or vacuum vapor deposition.

  Moreover, in order to form the Al alloy film by the sputtering method, the target includes the elements (1) to (3) described above (preferably those containing a rare earth element), and a desired target. If an Al alloy sputtering target having the same composition as the Al alloy film is used, there is no fear of composition deviation, and an Al alloy film having a desired component composition can be formed.

  Therefore, the present invention also includes a sputtering target having the same composition as the Al alloy film described above within the scope of the present invention. Specifically, the target includes Ni and / or Co elements belonging to Group A of 0.5 atomic% or less (excluding 0 atomic%), Ge of 0.2 to 2.0 atomic%, The element of Y and / or Zr belonging to Group B contains 3 atomic% or less (not including 0 atomic%), and the balance is Al and inevitable impurities. Moreover, as a preferable aspect, (a) Ni as an element belonging to the group A is 0.5 atomic% or less (excluding 0 atomic%); Ge is 0.2 to 2.0 atomic%; A target containing 1 to 3 atomic% of Y as an element belonging to B, the balance being Al and unavoidable impurities, and (a) at least one selected from the group consisting of La, Nd, and Gd. Examples include targets containing 5 atomic% or less (not including 0 atomic%).

  The shape of the target includes those processed into an arbitrary shape (such as a square plate shape, a circular plate shape, or a donut plate shape) according to the shape or structure of the sputtering apparatus.

  As a method for producing the above target, a method of producing an ingot made of an Al-based alloy by a melt casting method, a powder sintering method, or a spray forming method, or a preform made of an Al-based alloy (the final dense body is prepared) Examples thereof include a method obtained by producing an intermediate before being obtained) and then densifying the preform by a densification means.

  The present invention also includes a display device characterized in that the Al alloy film is used in a thin film transistor. As an aspect of the display device, the Al alloy film includes a source electrode and / or a drain electrode of a thin film transistor and a signal. Examples include those used for lines and having drain electrodes directly connected to transparent conductive films, and those used for gate electrodes and scanning lines.

  Further, the gate electrode and the scanning line, the source electrode and / or the drain electrode, and the signal line are included in the form of an Al alloy film having the same composition.

  The transparent pixel electrode of the present invention is preferably indium tin oxide (ITO) or indium zinc oxide (IZO).

  In manufacturing the display device provided with the Al alloy film of the present invention, a general process of the display device can be adopted. For example, the manufacturing method described in Patent Documents 1 and 2 described above may be referred to. .

  EXAMPLES 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 appropriate modifications are made within a range that can meet the above and the following purposes. 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 formed by DC magnetron sputtering (substrate = glass substrate (Eagle 2000 manufactured by Corning), atmosphere gas = argon, pressure = 2 mTorr, substrate temperature = 25). [Degree. C. (room temperature)].

  For the formation of the Al alloy films having various alloy compositions, Al alloy sputtering targets having various compositions prepared by vacuum melting were used.

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

  Using the Al alloy film formed as described above, the electrical resistivity of the Al alloy film itself after the heat treatment, the contact resistance with ITO when the Al alloy film is directly connected to the transparent pixel electrode (hereinafter referred to as “contact”) Abbreviated as “resistance”), and corrosion resistance and alkaline developer corrosion resistance and stripping solution corrosion resistance were measured by the following methods, respectively.

(1) Electric resistivity of the Al alloy film itself after the heat treatment A line and space pattern having a width of 10 μm is formed on the Al alloy film, and heated at a heating rate of 5 ° C./min in an inert gas atmosphere. After heat treatment at 320 ° C. for 30 minutes, the electrical resistivity was measured by the 4-terminal method. And the quality of the electrical resistivity of Al alloy film itself after heat processing was determined on the following reference | standard.
(Criteria)
○: 6.5 μΩ · cm or less ×: More than 6.5 μΩ · cm

(2) Contact resistance with the transparent pixel electrode The contact resistance when the Al alloy film and the transparent pixel electrode are in direct contact is the transparent pixel electrode (ITO; indium tin oxide in which 10 atomic% tin oxide is added to indium oxide). The Kelvin pattern (contact hole size: 10 μm square) shown in FIG. 5 was prepared by sputtering under the following conditions, and four-terminal measurement (current was passed through the ITO-Al alloy film and between the ITO-Al alloys at another terminal) The method of measuring the voltage drop) was performed. Specifically, the current I is passed between I _{1 and} I ₂ in FIG. 5 and the voltage V between V _{1 and} V ₂ is monitored, whereby the contact resistance R of the contact portion C is reduced to [R = (V ₂ − was determined as V ₁₎ / I _2]. And the quality of contact resistance was determined on the following reference | standard. The contact resistance of the pure Al alloy film is 15,000Ω.
(Conditions for forming transparent pixel electrodes)
・ Atmosphere gas = Argon ・ Pressure = 0.8 mTorr
-Substrate temperature = 25 ° C (room temperature)
(Criteria)
○: Less than 1000Ω ×: 1000Ω or more

(3) Stripping solution corrosion resistance The black spots (exactly crater corrosion density) generated after cleaning the stripping solution were observed to evaluate the stripping solution corrosion resistance. This black spot is generated around the precipitate with the precipitate as the base point as described above.

Specifically, for the sample obtained by performing the heat treatment, an amine resist stripping solution (TOK106) manufactured by Tokyo Ohka Kogyo Co., Ltd. is used (immersion in a stripping solution aqueous solution adjusted to pH = 10.5 for 1 minute) → (Processed for 5 minutes in an aqueous stripping solution adjusted to pH = 9.5) → (Rinse with pure water) → (Dry). The sample after stripping solution cleaning process was observed at a magnification of 1000 times optical microscope ⁽² about 8600μm), by performing image analysis to measure the black dot density (number / 100 [mu] m ^2).
(Criteria)
○: 7 or less / 100 μm ²
×: More than 7/100 μm ²

(4) Developer corrosion resistance After masking a part of the Al alloy film in a film formation state (no subsequent heat treatment) and immersing in a developer (solution containing 2.38% by mass of TMAH) for 1 minute, The plate was washed with pure water for 1 minute and dried by blowing N ₂ gas. Then, the masking was peeled off, and the level difference between the test part and the masking part (non-test part) was measured at three locations using a palpation type step gauge, and the etching rate (nm / min) was calculated using the average value as the etching amount. . Then, the developer corrosion resistance of the Al alloy film was evaluated according to the following criteria.
A: Less than 50 nm / min. O: 50 nm or more and 100 nm or less / min. X: More than 100 nm / min.

(5) Measurement of deposits The deposited sample was subjected to a heat treatment (heating at 320 ° C. for 30 minutes in a nitrogen flow) simulating a thermal history applied when the TFT substrate was formed, thereby depositing precipitates.

The precipitate thus deposited is observed with a planar TEM (magnification of 300,000 times), and a precipitate composed only of Al and Ni and / or a precipitate composed only of Al and Co (acceleration voltage 1 keV ( The equivalent circle diameter of the precipitates seen in the vicinity of the surface) was calculated and used as the particle size of the precipitates. The number of precipitates having a particle size of more than 100 nm observed during 10,000-fold reflection SEM observation (10 μm × 12.5 μm / field total 3 fields) was calculated and converted to the number per 100 μm ² . Here, the number of Al ₃ Ni as a precipitate composed only of Al and Ni and the number of Al ₉ Co ₂ as a precipitate composed only of Al and Co were determined and converted.

As described above, this precipitate and the black spot described in the above (3) are particularly closely related. Specifically, the acceptance criteria for sunspot density (7 or less / 100 μm ² ) is the number of Al ₃ Ni (pieces / 100 μm ² ) ≦ 4.0 or the number of Al ₉ Co ₂ (pieces / 100 μm ² ) ≦ It almost corresponds to 1.0.

  These results are shown in Table 1. In the composition of each Al alloy film shown in Table 1, the balance is Al and inevitable impurities.

  From the results of Table 1, it can be considered as follows.

  First, No. 1 containing Co as an element of group A was obtained. Consider 1-10.

  Among these, No. further containing Group B elements. Nos. 1 to 6 not only achieved reduction in contact resistance with ITO (all not shown in the table, o), but also reduced electrical resistivity after heat treatment, as well as developer corrosion resistance and stripping solution corrosion resistance. It turns out that it is excellent in both. Specifically, no. 1, 3, 4 are examples including Y as group B; 2, 5, and 6 are examples containing Zr as group B, and good chemical solution corrosion resistance was obtained when any element was used. No. Nos. 3 to 6 are examples in which a rare earth element was further added, and generation of hillocks after heat treatment could be prevented (not shown in the table).

  On the other hand, no. In all of Nos. 7 to 10, the sunspot density increased and the stripping solution corrosion resistance decreased.

  No. 8 and 9 were examples in which no Ge was added, and the contact resistance was increased as compared with the Ge-added example (not shown in the table).

  The tendency similar to the above (effect of improving chemical corrosion resistance by adding elements of group B) is the same as that of group No. containing Ni instead of Co as an element of group A. It was recognized also about 11-22.

  That is, No. further including Group B elements. Nos. 11 to 20 not only achieved reduction in contact resistance with ITO (not shown in the table, all ◯) and reduction in electrical resistivity of the Al alloy after heat treatment, but also developed solution corrosion resistance and Excellent in both stripping solution corrosion resistance. Specifically, no. Nos. 11, 13 to 16, 19, and 20 further contain Y as group B; Nos. 12, 17 and 18 are examples further containing Zr as group B, and good chemical solution corrosion resistance was obtained when any element was used. No. Nos. 13 to 20 are examples in which a rare earth element was further added, and generation of hillocks could be prevented (not shown in the table).

Among the above examples, Y is 1 atomic% or more, and the ratio (β / α) of the content (β) of the element belonging to Group B to the content (α) of the element belonging to Group A is more than 7. No. 11, 15, 16, 19, and 20, the sunspot density is 0.2 or less / 100 μm ² and the number of precipitates is 0.1 or less / 100 μm ² ). It can be seen that the stripping solution is extremely excellent in corrosion resistance. Moreover, in these examples, the electrical resistivity is also kept low. Therefore, it was confirmed that the Al—Ni—Ge alloy film containing 1 to 3 atomic% of Y is extremely useful as an Al alloy film for a display device particularly excellent in the effect of suppressing the sunspot density. The same effect is also seen when Co is used instead of Ni, and an extremely good black spot density suppressing effect is also obtained for an Al—Co—Ge alloy film containing 1 to 3 atomic% of Y. Was obtained (not shown in the table).

  On the other hand, no. Nos. 21 and 22 can reduce the contact resistance with ITO (transparent pixel electrode) by adding Ni and Ge (not shown in the table), but in both cases, the black spot density increased and the stripping solution corrosion resistance decreased.

Claims (10)

An Al alloy film directly connected to the transparent conductive film on the substrate of the display device,
In the Al alloy film, an element of Ni and / or Co belonging to group A is 0.5 atomic% or less (excluding 0 atomic%), Ge is 0.2 to 2.0 atomic%, group B Al alloy film for display device excellent in corrosion resistance and developer corrosion resistance in stripping solution cleaning, characterized by containing Y and / or Zr element belonging to 1 and 3 atom% or less (not including 0 atom%) .   Ni is 0.5 atomic% or less (not including 0 atomic%) as an element belonging to the group A, Ge is 0.2 to 2.0 atomic%, and Y is 1 to 1 as an element belonging to the group B. The Al alloy film for a display device according to claim 1, comprising 3 atomic%.   The ratio (β / α) between the content (β) of the element belonging to the group B and the content (α) of the element belonging to the group A satisfies 0.5 or more and 7 or less. 2. Al alloy film for display device according to 2.   The ratio (β / α) of the content (β) of the element belonging to the group B and the content (α) of the element belonging to the group A satisfies 7 or more. Al alloy film for display devices. The equivalent circle diameter exceeds 100 nm, and the number of precipitates composed only of Al and Ni and / or the precipitate composed only of Al and Co is 4.0 or less per 100 μm ² . 4. The Al alloy film for a display device according to any one of 4 above.   Furthermore, at least 1 type selected from the group which consists of La, Nd, and Gd is 0.5 atomic% or less (it does not contain 0 atomic%), Al for display apparatuses in any one of Claims 1-5. Alloy film.   7. A display device, wherein the Al alloy film for a display device according to claim 1 is used for a thin film transistor.   An Al alloy sputtering target used for forming an Al alloy film that is directly connected to a transparent conductive film on a substrate of a display device, wherein the Al alloy contains Ni and / or Co elements belonging to Group A in an amount of 0.1%. 5 atomic% or less (excluding 0 atomic%), Ge 0.2 to 2.0 atomic%, and Y and / or Zr elements belonging to group B 3 atomic% or less (including 0 atomic%) And a balance of Al and inevitable impurities.   Ni is 0.5 atomic% or less (not including 0 atomic%) as an element belonging to the group A, Ge is 0.2 to 2.0 atomic%, and Y is 1 to 1 as an element belonging to the group B. The sputtering target according to claim 8, comprising 3 atomic% and the balance being Al and inevitable impurities.   Furthermore, the sputtering target of Claim 8 or 9 which contains 0.5 atomic% or less (0 atomic% is not included) of at least 1 type selected from the group which consists of La, Nd, and Gd.