JP2010165865A - Al-ALLOY FILM FOR DISPLAY DEVICE, DISPLAY DEVICE, AND Al-ALLOY SPUTTERING TARGET - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an Al-alloy film for a display device in which contact resistance with a transparent pixel electrode directly connected with the Al-alloy film is sufficiently reduced and corrosion resistance and heat resistance are improved. <P>SOLUTION: The Al-alloy film is directly connected with a transparent conductive film on a substrate of a display device. The Al-alloy film contains ≤0.5 atom% (not including 0 atom%) of Co, 0.2-2.0 atom% of Ge, and ≤0.5 atom% (not including 0 atom%) of Cu. The Al-alloy film is configured such that a total amount of Co, Ge, and Cu is 0.2-2.0 atom% while satisfying formula (1): Cu/Co≤1.5 or formula (2): 2.5≤Cu/Co≤6.0. In formulas (1), (2), Cu and Co represent a content (atom%) of each element in the Al-alloy film, respectively. <P>COPYRIGHT: (C)2010,JPO&INPIT

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, an Al alloy film excellent in corrosion resistance and heat resistance, a display device using the Al alloy film for a thin film transistor, and The present invention relates to 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 resistance 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”). In some cases, a direct contact technique has been proposed in which the Al alloy wiring itself has a small electrical resistance and is excellent in heat resistance. 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 resistance of the wiring itself can be kept low. . It also describes that heat resistance can be improved by adding rare earth elements such as La, Nd, Gd, and Dy. Furthermore, 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 is required to have both excellent contact resistance with the transparent pixel electrode and low wiring resistance as well as better corrosion resistance. . 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 precipitates containing alloy elements are formed in the Al matrix in the course of this thermal history. Since the potential difference between the 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 ionization and elution cause pitting corrosion (black spots, corrosion marks) to be formed. When the pitting corrosion occurs, the transparent pixel electrode (ITO film) becomes discontinuous, which may adversely affect long-term reliability.

  In the photolithography process, an alkaline developer containing, for example, TMAH (tetramethylammonium hydroxide) is used. However, in the case of the direct contact structure, the barrier metal layer is omitted, and the Al alloy film is exposed. Susceptible to liquid damage (thinning of Al alloy film). In particular, when the amount of Co is reduced (for example, 0.1 atomic% or less) with emphasis on the suppression of the etching rate of the Al alloy film by the developer, the heat resistance is reduced and hillocks (cove-like projections) , Which can be recognized as a black spot when observed with an optical microscope). This hillock is also a factor that makes the ITO film described above discontinuous.

  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 resistance against an organic stripping solution. In particular, as described later, when Co is contained as an element effective for ensuring low contact resistance, it is difficult to ensure corrosion resistance or heat resistance, and the ITO film is likely to be discontinuous. There is, however, no focus on such problems.

  The present invention has been made paying attention to the above circumstances, and its purpose is to eliminate the barrier metal layer and to ensure low contact resistance when directly connected to the transparent pixel electrode, in particular, Al containing Co. As for the alloy film, the corrosion resistance (in the present invention, “resistance to the developer and stripping solution used in the manufacturing process of the display device”) is sufficiently improved and the occurrence of the hillock is suppressed, thereby preventing the discontinuity of the ITO film. The object is to realize a highly reliable display device.

The Al alloy film for a display device according to the present invention is an Al alloy film directly connected to a transparent conductive film on a substrate of the display device, and Co is 0.5 atomic% or less (not including 0 atomic%). ), 0.2 to 2.0 atomic% of Ge, and 0.5 atomic% or less (not including 0 atomic%) of Cu, and the total amount of Co, Ge and Cu is 0.2 to 2.0 atomic% % And is characterized by satisfying the following formula (1) or formula (2).
Cu / Co ≦ 1.5 (1)
2.5 ≦ Cu / Co ≦ 6.0 (2)
(In the formulas (1) and (2), Cu and Co indicate the content (atomic%) of each element in the Al alloy film)

  The Al alloy film preferably has a maximum precipitate particle size of 60 nm or less, and preferably has an average crystal particle size of 100 nm or less.

  When the Co content of the Al alloy film is more than 0.1 atomic% and 0.5 atomic% or less, the formula (1) is satisfied, and the total amount of Co, Ge, and Cu is 0.3-2. It is preferably 0.0 atomic%. Further, when the Co content of the Al alloy film is 0.1 atomic% or less (not including 0 atomic%), it is preferable to satisfy the formula (2).

  The Al alloy film further contains at least one element selected from the group consisting of La, Y, Nd, and Gd in an amount of 0.1 to 0.5 atomic% (when a plurality of elements are included, the total amount is referred to). ) May be included.

  The present invention also includes a display device in which the Al alloy film is used in a thin film transistor.

The present invention also provides a sputtering target used for forming an Al alloy film directly connected to a transparent conductive film on a substrate of a display device, wherein Co is 0.5 atomic% or less (excluding 0 atomic%). ), 0.2 to 2.0 atomic% of Ge, and 0.5 atomic% or less (not including 0 atomic%) of Cu, and the total amount of Co, Ge and Cu is 0.2 to 2.0 atomic% %, And also satisfies the following formula (1) or formula (2), and the Al alloy sputtering target is characterized in that the balance is Al and inevitable impurities.
Cu / Co ≦ 1.5 (1)
2.5 ≦ Cu / Co ≦ 6.0 (2)
(In formulas (1) and (2), Cu and Co indicate the content (atomic%) of each element in the Al alloy sputtering target)

  When the Co content of the Al alloy sputtering target is more than 0.1 atomic% and 0.5 atomic% or less, the above formula (1) is satisfied, and the total amount of Co, Ge, and Cu is 0.3 to What is 2.0 atomic% is preferable. Moreover, when Co content of the said Al alloy sputtering target is 0.1 atomic% or less (it does not contain 0 atomic%), what satisfy | fills said Formula (2) is preferable.

  The Al alloy sputtering target further contains at least one element selected from the group consisting of La, Y, Nd, and Gd in an amount of 0.1 to 0.5 atomic% (when a plurality of elements are included, the total amount is It may be included).

  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 corrosion resistance (stripping solution resistance, developer) It is possible to provide an Al alloy film having excellent resistance (particularly, stripping solution resistance) and heat resistance. When the Al alloy film of the present invention is applied to a display device, discontinuity of the ITO film is suppressed and a highly reliable display device can be obtained. In addition, since the barrier metal layer can be omitted, an inexpensive display device with excellent productivity can be obtained.

It is the graph which showed the relationship between the precipitate diameter and the corrosion diameter about each of the Al-Ni-Ge-type alloy film and the Al-Co-Ge-type alloy film. It is the graph which showed the relationship between Cu / Co of Al alloy film, and the particle size of the largest precipitate. It is the graph which showed the relationship between Cu / Co (Co = 0.1 atomic%) of an Al alloy film, and a sunspot density.

  In putting the direct contact technology into practical use, the Al alloy film is required to exhibit low contact resistance and low wiring resistance as well as exhibit excellent corrosion resistance and heat resistance as described above.

  In particular, in order to increase the corrosion resistance, the particle size of precipitates (precipitate size) present in the Al alloy film is almost proportional to the particle size of corrosion marks (corrosion diameter) caused by the precipitates. It has been found as a knowledge that the precipitate diameter should be reduced and the corrosion diameter should be reduced to a level that is practically acceptable. For example, when the Al—Ni-based alloy film proposed in the direct contact technique is examined for a layer in which corrosion is suppressed to a level where there is no practical problem, the precipitate diameter is approximately 250 nm or less. In particular, it has been proposed that in an Al—Ni—Ge-based alloy film, the precipitate diameter can be further reduced to 100 nm or less, and corrosion starting from the precipitate can be further reduced.

  On the other hand, in an Al—Co—Ge alloy film containing Co and further Ge as an element useful for ensuring low contact resistance, the precipitate diameter is the same as that of the Al—Ni—Ge alloy film. It has been found that even if it is reduced, the corrosion resistance cannot be sufficiently improved as much as the Al—Ni—Ge alloy film.

  FIG. 1 shows an Al-0.2 (atomic%) Ni-0.5 (atomic%) Ge-0.2 (atomic%) La alloy film and an Al-0.2 (atomic%) Co-0.5 ( Atomic%) Ge-0.2 (atomic%) The particle size of precipitates (precipitate diameter) present in the La alloy film, and after immersing these Al alloy films in the stripping solution as shown in the examples described later The relationship of the diameter (corrosion diameter) of the corrosion mark (it is considered to originate in the said deposit) which arises is shown. From FIG. 1, in the case of an Al—Ni—Ge based alloy film, the corrosion diameter can be made substantially zero and the corrosion resistance can be remarkably improved by controlling the precipitate diameter to 100 nm or less (FIG. 1 (a )) In the case of an Al—Co—Ge-based alloy film, it can be seen that even if the precipitate diameter is controlled to 100 nm or less, the corrosion diameter is hardly reduced and the corrosion resistance is not sufficiently improved (FIG. 1 (b)).

  Therefore, the present inventors have sufficiently improved the corrosion resistance of the Al alloy film, and also improved the heat resistance to suppress the generation of hillocks, particularly for the Al alloy film containing Co in order to realize a low contact resistance. As a result of intensive research, it has been found that an appropriate amount of Cu may be contained together with a specified amount of Co and Ge, and the balance between the Co amount and the Cu amount should be balanced. Hereinafter, the Al alloy film of the present invention will be described in detail.

  First, the Al alloy film of the present invention contains Co in a range of 0.5 atomic% or less (not including 0 atomic%) in order to ensure low contact resistance. In order to surely keep the contact resistance low, Co is preferably contained in an amount of 0.02 atomic% or more, more preferably 0.05 atomic% or more. However, if the amount of Co is excessive, the corrosion resistance is lowered, so the Co amount is 0.5 atomic% or less. Preferably it is 0.3 atomic% or less.

  Moreover, the Al alloy film of the present invention contains 0.2 to 2.0 atomic% of Ge. Ge is also an element necessary for ensuring low contact resistance. 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 crystal grain boundary, which effectively acts on the refinement of Al crystal grains, and as a result, contributes to the refinement of precipitates as described later. In order to exhibit the effect sufficiently, 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 resistance 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.

  Furthermore, the Al alloy film of the present invention contains Cu in a range of 0.5 atomic% or less (not including 0 atomic%). Cu has the effect of promoting the formation of composite precipitates with Co and the like, and suppressing the diffusion of Co. By suppressing the formation of composite precipitates and the growth of Co-based precipitates, the precipitates are refined. Is an effective element. When the amount of Co is relatively small, Cu acts effectively as a heat resistance improving element. In order to sufficiently exhibit such an effect, Cu is preferably contained at 0.05 atomic% or more, more preferably 0.1 atomic% or more. In particular, when the Co content is 0.1 atomic% or less, Cu is preferably 0.2 atomic% or more.

  However, when Cu is excessively contained, Cu-rich coarse precipitates are easily formed, and the corrosion resistance is decreased. Therefore, in this invention, the amount of Cu shall be 0.5 atomic% or less. Preferably it is 0.4 atomic% or less.

The Al alloy film of the present invention also satisfies the following formula (1) or formula (2).
Cu / Co ≦ 1.5 (1)
2.5 ≦ Cu / Co ≦ 6.0 (2)
(In the formulas (1) and (2), Cu and Co indicate the content (atomic%) of each element in the Al alloy film)

  By satisfying the above formula (1) or (2), it is possible to exhibit excellent corrosion resistance and suppress corrosion caused by precipitates. In addition, excellent heat resistance can be exhibited to suppress the generation of hillocks.

  In order to ensure the above effects, it is preferable to satisfy the above formula (1) when the Co content is more than 0.1 atomic% and 0.5 atomic% or less. When the amount of Co is relatively large, a precipitate having a relatively large particle size is easily formed as described above, but a fine composite precipitate is formed by adding Cu. However, when an excessive amount of Cu is present relative to Co, a coarse precipitate rich in Cu is formed as described above, and this tends to be a starting point of corrosion. FIG. 2 shows the amount of Co in Al—Co—0.5 atomic% Ge—Cu—0.2 atomic% La (in the range of more than 0.1 atomic% to 0.5 atomic% or less) and the Cu amount (atomic%). 5 is a graph showing the relationship between Cu (atomic%) / Co (atomic%) and the particle size of the maximum precipitate of each Al alloy film in various Al alloy films with different values. From FIG. 2, it can be seen that when the Co content is more than 0.1 atomic% and 0.5 atomic% or less, the inclusion of Cu makes the maximum precipitate particle size smaller than when Cu is not included. . However, it can also be seen that when the amount of Cu is excessive with respect to the amount of Co, the particle size of the maximum precipitate increases rapidly.

  In the case of the Al alloy film containing Co, Ge and Cu of the present invention, if the precipitate diameter is 60 nm or less, the corrosion diameter becomes small, that is, the corrosion resistance can be sufficiently improved. Is more than 0.1 atomic% and 0.5 atomic% or less, Cu / Co is preferably 1.5 or less (not including 0). From the viewpoint of further improving the corrosion resistance by reducing the precipitate diameter to 50 nm or less, the lower limit of Cu / Co is preferably 0.2, and the upper limit of Cu / Co is more preferably 1.3. preferable.

  On the other hand, when the amount of Co is 0.1 atomic% or less (excluding 0 atomic%), it is preferable to satisfy the formula (2). When the amount of Co is relatively small in this way, the heat resistance is reduced due to the small amount of Co, and hillocks are likely to occur. Due to this hillock, the resistance to the stripping solution is deteriorated (that is, black spots due to hillocks are reduced). Increase) or discontinuity of the ITO film. Therefore, when the Co content is 0.1 atomic% or less, it is desirable to ensure heat resistance by relatively increasing Cu, and Cu / Co is set to 2.5 or more. From the viewpoint of suppressing the generation of hillocks, when the Co content is 0.1 atomic% or less, Cu / Co is more preferably 3 or more.

FIG. 3 shows examples of various Al alloy films in which the Cu amount (atomic%) of Al-0.1 atomic% Co-0.5 atomic% Ge-Cu-0.2 atomic% La is changed. As shown in the figure, the sample was immersed in a stripping solution and observed with an optical microscope (magnification: 1000 times) for one field of view (field size of about 12000 μm ² ). Is a graph showing the relationship between the density converted to the density per 100 μm ² (spot density) and Cu (atomic%) / Co (atomic%). From FIG. 3, when the Co amount is 0.1 atomic% or less, the black spot density is decreased by increasing Cu / Co, and the black spot density is sufficiently decreased by increasing Cu / Co to 2.5 or more. I understand that I can do it. In addition, it is considered that the black spots in FIG. 3 include some of those caused by corrosion marks in addition to those caused by the hillocks.

  Even when the amount of Co is 0.1 atomic percent or less (excluding 0 atomic percent), if the amount of Cu is excessive with respect to the amount of Co, a Cu-rich coarse precipitate is formed, which tends to be a starting point for corrosion. Conceivable. Therefore, Cu / Co is suppressed to 6.0 or less. The preferable upper limit of Cu / Co when the amount of Co is 0.1 atomic% or less (not including 0 atomic%) is 5.5.

  In the Al alloy film of the present invention, the total amount of Co, Ge and Cu satisfies 0.2 to 2.0 atomic%.

  From the viewpoint of securing the contact property with the ITO film and from the viewpoint of sufficiently exhibiting the effect of fine precipitates by containing Cu, the total amount of Co, Cu and Ge needs to be a certain level or more. In the present invention, the total amount of Co, Cu and Ge is 0.2 atomic% or more. In particular, when the Co content is more than 0.1 atomic% and 0.5 atomic% or less, the lower limit of the total amount of Co, Ge, and Cu is set to 0.3 atomic% in order to fully exhibit the above effect. Is preferred. Regardless of the amount of Co, the more preferable lower limit of the total amount of Co, Ge and Cu is 0.7 atomic%. On the other hand, if the total amount of these elements is excessive, the electrical resistance of the Al alloy film itself increases or the corrosion resistance decreases. Therefore, the total amount of Co, Cu and Ge is set to 2.0 atomic% or less, preferably 1.2 atomic% or less.

  By satisfying the above component composition and controlling the thermal history of the Al alloy film in the manufacturing process of the display device to a recommended condition as described later, the maximum precipitate particle size in the Al alloy film is 60 nm or less. Corrosion can be reduced to a level where there is no practical problem. The Al alloy film of the present invention preferably has an average crystal grain size (average grain size of Al crystal grains) of 100 nm or less. Since the basic precipitation site of the precipitate is the grain boundary triple point, if the average grain size of the Al crystal grains is reduced and many grain boundary triple points exist, the number of precipitation sites increases and the precipitate diameter decreases. Conceivable. The precipitate includes at least one of Co, Cu, Ge, and La. Further, the particle size of the maximum precipitate and the average crystal particle size of the Al alloy film are measured by the methods shown in Examples described later.

  The Al alloy film of the present invention contains the above elements as basic components, and the balance is Al and inevitable impurities.

  Furthermore, 0.1 to 0.5 atomic% (in the case of containing a plurality of elements) of at least one element selected from the group consisting of La, Y, Nd, and Gd (hereinafter sometimes referred to as La). It is also possible to use an Al alloy film containing the total amount. La and the like have the effect of suppressing the formation of hillocks and increasing the heat resistance. Further, it is an element effective for suppressing the etching rate of the Al alloy film in the developer step, that is, for improving the resistance of the Al alloy film to the developer. In order to effectively exhibit these effects, it is preferable to contain La at 0.1 atomic% or more, and more preferably 0.2 atomic% or more. However, when the content of La or the like becomes excessive, the electrical resistance of the Al alloy film itself increases. Therefore, the preferable upper limit of the content of La and the like is 0.5 atomic% (more preferably 0.4 atomic%).

  Of the La and the like, La, Nd, and Gd are preferable, and Nd is more preferable.

  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.

  Further, in order to form the Al alloy film of the present invention by the sputtering method, if an Al alloy sputtering target having the same composition as the desired Al alloy film is used, the Al alloy film having a desired component / composition can be obtained without misalignment. It is good because it can be formed.

  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 for producing an ingot made of an Al alloy by a melting casting method or a powder sintering method, or a preform made by an Al alloy by a spray forming method (before obtaining a final dense body) Examples thereof include a method obtained by producing the intermediate) and then densifying the preform by a densifying means.

  The Al alloy film of the present invention is used for a source electrode and / or a drain electrode and a signal line of a thin film transistor, and the drain electrode is preferably directly connected to the transparent conductive film. The Al alloy film of the present invention can also be used for gate electrodes and scanning lines. In this case, it is preferable that the source electrode and / or the drain electrode and the signal line, and the gate electrode and the scanning line are made of an Al alloy film having the same composition.

  The present invention includes a TFT substrate using the Al alloy film as a thin film transistor and a display device including the TFT substrate. The present invention is characterized by specifying the component composition of the Al alloy film, and the requirements for configuring the TFT substrate and the display device other than the Al alloy film are not particularly limited as long as they are normally used. For example, examples of the transparent pixel electrode used in the present invention include an indium tin oxide (ITO) film and an indium zinc oxide (IZO) film.

  The heat treatment of the Al alloy film in the conventional direct contact technique is roughly performed in an atmosphere having a maximum attained temperature of 300 to 350 ° C., a holding time of 10 to 40 minutes, and a rate of temperature rise to the maximum attained temperature of 5 to 60 ° C./minute. Done on condition. However, in the present invention, it is preferable to make the rate of temperature rise to the maximum temperature lower than the heat treatment conditions of the conventional Al alloy film. That is, the Al alloy film formed by sputtering is in a supersaturated solid solution state in the as-depo state (immediately after the film formation), and precipitation of the additive element is started by applying heat. Since the basic precipitation site of the precipitate is a grain boundary triple point, it is considered that the finer the Al crystal grains, the more precipitation sites and the smaller the precipitate diameter. On the other hand, Al crystal grains grow and become coarse as the heat treatment temperature rises. Therefore, in order to deposit fine precipitates, it is preferable to deposit before the start of Al grain growth (in the temperature range where the Al crystal grains are fine), so the rate of temperature rise until reaching the maximum temperature is increased. It is preferable to make it as late as possible. In the present invention, as the recommended conditions, for example, the maximum temperature reached: 330 ° C. ± 10 ° C., the retention time at the maximum temperature reached: about 30 minutes, and the heating rate up to the maximum temperature: about 5 ° C./minute. Can be mentioned.

  In manufacturing a display device provided with an Al alloy film of the present invention, except that the conditions for heat treatment after the formation of the Al alloy film (including the thermal history after the formation of the Al alloy film) are the recommended conditions described above. What is necessary is just to employ | adopt the general process of a display apparatus, for example, what is necessary is just to refer to the manufacturing method of patent document 1 and 2 mentioned above.

  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)), sputtering gas = argon, pressure = 2 mTorr, substrate temperature = 25. (° 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 was determined by ICP emission analysis (inductively coupled plasma emission analysis).

  With respect to the obtained Al alloy film, the maximum precipitate particle size, the average crystal particle size of the Al alloy film, and the corrosion resistance (resistance to the stripping solution and resistance to the developer) were evaluated as follows. The maximum precipitate grain size and the average crystal grain size of the Al alloy film were measured with respect to those having excellent resistance to the developer and examples in which Ge was included and the contact resistance was low.

(A) Particle size of maximum precipitate Simulating the heat history applied to the above Al alloy film during TFT substrate fabrication, the rate of temperature rise to the maximum temperature in an N ₂ atmosphere: 5 ° C / min, the maximum temperature reached : Heat treatment was performed at 330 ° C. for 30 minutes to obtain a sample. Using the sample obtained by the above heat treatment, using a transmission electron microscope (TEM), two fields of view (one field size: 3 μm × 3 μm) at a magnification of 50,000 times by high angle scattering dark field method (HAADF) Observed and photographed all deposits in the field of view. Then, image analysis was performed to determine the size distribution of the precipitate, and the maximum diameter (the maximum particle size of the precipitate) was determined.

(B) Average crystal grain size of Al alloy film (average grain size of Al crystal grains)
About the sample obtained by performing the said heat processing, it calculated | required by the cutting method (JISH0501) using the said TEM observation photograph.

(C) Resistance to stripping solution For the sample obtained by performing the heat treatment, an amine-based resist stripping solution (TOK106) manufactured by Tokyo Ohka Kogyo Co., Ltd. was used for 1 minute in a stripping solution aqueous solution adjusted to pH = 10.5. Immersion) → (Immersion for 5 minutes in an aqueous stripping solution adjusted to pH = 9.5) → (Wash with pure water) → (Dry). When the sample after the treatment was observed with an optical microscope at a magnification of 1000 times, the occurrence of black spots was Al-0.2 atomic% Co-0.5 atomic% Ge- which is a reference material (ref. Material). A film superior to the 0.2 atomic% La alloy film was marked with ◯, an equivalent film was marked with Δ, and a bad film was marked with x.

(D) Resistance to developer After masking a part of the as-depo Al alloy film and immersing it in a developer kept at 30 ° C. (solution containing 2.38% by mass of TMAH) for 1 minute, 1 with pure water Washed for minutes and sprayed with N ₂ gas to dry. 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 points using a palpation type step gauge, and the etching rate was calculated using the average value as the etching amount. And the tolerance with respect to the developing solution of Al alloy film was evaluated by the following reference | standard.
○ (Excellent resistance to developer): Etching rate is 150 nm / min or less × (Inferior to developer): Etching rate exceeds 150 nm / min These results are shown in Table 1.

  From Table 1, it can be considered as follows. That is, Examples 1 to 7 of the present invention satisfy the specified conditions, so that the precipitate diameter is fine, and excellent resistance to both the stripping solution and the developing solution was obtained. In addition, hillocks were not confirmed for these inventive examples.

  On the other hand, in Comparative Example 1, since the amount of Cu was excessive and Cu / Co exceeded the upper limit, extremely coarse precipitates were formed, resulting in extremely poor resistance to the stripping solution.

  Since Comparative Example 2 did not contain Cu, the maximum precipitate particle size exceeded 60 nm. Further, since Comparative Example 3 does not contain Cu and Ge, compared with Comparative Example 2, the effect of refining Al crystal grains by Ge is not exerted, and precipitates having a remarkably large particle size are generated. It was inferior in resistance to.

  In Comparative Example 4, since Co was excessively contained and Cu and Ge were not included, both the resistance to the stripping solution and the resistance to the developer were inferior.

  Since Comparative Example 5 did not contain Cu and Ge, the result was inferior in resistance to the stripping solution.

  From Comparative Example 6, it can be seen that when the amount of Co is relatively small, Cu / Co is preferably set to 2.5 or more in order to increase the resistance to the stripping solution.

  As specified in the present invention, the Al alloy film containing Co and Ge exhibits a low contact resistance. In order to confirm this, as shown in Examples of Patent Documents 1 and 2, the Al alloy film is transparent. When the contact resistance with the ITO film constituting the pixel electrode was measured, it was as high as 5000Ω in the comparative example 5 not including Ge, whereas all the Al alloy films including a specified amount of Ge were as low as 1000Ω or less. The contact resistance was confirmed.

Claims (11)

An Al alloy film directly connected to the transparent conductive film on the substrate of the display device,
The Al alloy film has Co of 0.5 atomic% or less (excluding 0 atomic%), Ge of 0.2 to 2.0 atomic%, and Cu of 0.5 atomic% or less (including 0 atomic%). And an Al alloy film for a display device, wherein the total amount of Co, Ge, and Cu is 0.2 to 2.0 atomic% and satisfies the following formula (1) or formula (2): .
Cu / Co ≦ 1.5 (1)
2.5 ≦ Cu / Co ≦ 6.0 (2)
(In the formulas (1) and (2), Cu and Co indicate the content (atomic%) of each element in the Al alloy film)   The Al alloy film for a display device according to claim 1, wherein the particle size of the maximum precipitate is 60 nm or less.   The Al alloy film for a display device according to claim 1, wherein an average crystal grain size of the Al alloy film is 100 nm or less.   The Co content is more than 0.1 atomic% and 0.5 atomic% or less, satisfies the formula (1), and the total amount of Co, Ge, and Cu is 0.3 to 2.0 atomic%. The Al alloy film for display devices according to claim 1.   The Al alloy film for a display device according to any one of claims 1 to 3, wherein the Co content is 0.1 atomic% or less (not including 0 atomic%) and satisfies the formula (2).   The Al alloy film for a display device according to any one of claims 1 to 5, further comprising 0.1 to 0.5 atomic% of at least one element selected from the group consisting of La, Y, Nd, and Gd. .   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 directly connected to a transparent conductive film on a substrate of a display device, wherein Co is 0.5 atomic% or less (excluding 0 atomic%), Ge is 0.2 to 2.0 atomic percent, and Cu is 0.5 atomic percent or less (excluding 0 atomic percent), the total amount of Co, Ge and Cu is 0.2 to 2.0 atomic percent, And Al alloy sputtering target characterized by satisfy | filling following formula (1) or Formula (2), and remainder being Al and an inevitable impurity.
Cu / Co ≦ 1.5 (1)
2.5 ≦ Cu / Co ≦ 6.0 (2)
(In formulas (1) and (2), Cu and Co indicate the content (atomic%) of each element in the Al alloy sputtering target)   The Co content is more than 0.1 atomic% and 0.5 atomic% or less, satisfies the formula (1), and the total amount of Co, Ge, and Cu is 0.3 to 2.0 atomic%. The Al alloy sputtering target according to claim 8.   The Al alloy sputtering target according to claim 8, wherein the Co content is 0.1 atomic% or less (excluding 0 atomic%) and satisfies the formula (2).   The Al alloy sputtering target according to any one of claims 8 to 10, further comprising 0.1 to 0.5 atomic% of at least one element selected from the group consisting of La, Y, Nd, and Gd.

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