JP5547574B2 - Al-based alloy sputtering target - Google Patents

Description

  The present invention relates to an Al-based alloy sputtering target, and more particularly to an Al-based alloy sputtering target capable of reducing initial splash that occurs in the initial stage of sputtering when a thin film is formed using the sputtering target. It is. The Al-based alloy targeted by the present invention is an Al-based alloy containing at least one selected from Group A (Ni, Co) and at least one selected from Group B (La, Nd); or Furthermore, it is an Al-based alloy containing at least one selected from Group C (Cu, Ge), and each Al-based alloy may further contain Ti and B. Hereinafter, the former Al-based alloy is referred to as “Al- (Ni, Co)-(La, Nd) -based alloy”, and the latter Al-based alloy is referred to as “Al- (Ni, Co)-(La, Nd). )-(Cu, Ge) -based alloy ”.

  An Al-based alloy has a low electrical resistivity and is easy to process. For this reason, a liquid crystal display (LCD), a plasma display panel (PDP), an electroluminescence display (ELD), and so on. Widely used in the fields of flat panel displays (FPD: Flat Panel Display), touch panels, and electronic paper, such as displays, field emission displays (FEDs), and micro electro mechanical systems (MEMS) displays. Film, electrode film, reflective electrode film, etc. It has been used in the material.

  For example, an active matrix liquid crystal display includes a TFT substrate having a thin film transistor (TFT) that is a switching element, a pixel electrode formed of a conductive oxide film, and a wiring including a scanning line and a signal line. The scanning lines and signal lines are electrically connected to the pixel electrodes. In general, pure Al or Al—Nd alloy thin films are used as the wiring material constituting the scanning lines and signal lines. However, when these thin films are brought into direct contact with the pixel electrodes, insulating aluminum oxide or the like is brought into the interface. In order to increase the contact electric resistance, a barrier metal layer made of a refractory metal such as Mo, Cr, Ti, or W has been provided between the Al wiring material and the pixel electrode so far. Has been reduced.

  However, the method of interposing a barrier metal layer as described above has problems such as a complicated manufacturing process and an increase in production cost.

  Therefore, the present applicant provides a technique (direct contact technique) that can directly contact the conductive oxide film constituting the pixel electrode with the wiring material without using the barrier metal layer. A method using an Al—Ni alloy or a thin film of an Al—Ni—rare earth element alloy further containing a rare earth element such as Nd or Y has been proposed (Patent Document 1). If an Al—Ni alloy is used, conductive Ni-containing precipitates and the like are formed at the interface, and generation of insulating aluminum oxide and the like is suppressed, so that the contact electrical resistance can be kept low. In addition, if an Al—Ni—rare earth element alloy is used, the heat resistance is further enhanced.

  By the way, generally the sputtering method using a sputtering target is employ | adopted for formation of an Al group alloy thin film. In the sputtering method, a plasma discharge is formed between a substrate and a sputtering target composed of the same material as the thin film material, and a gas ionized by the plasma discharge is made to collide with the sputtering target, thereby causing the atoms of the sputtering target to collide. It is a method of producing a thin film by knocking out and laminating on a substrate.

  Unlike the vacuum deposition method, the sputtering method has an advantage that a thin film having the same composition as the sputtering target can be formed. In particular, an Al-based alloy thin film formed by a sputtering method can dissolve an alloy element such as Nd that does not form a solid solution in an equilibrium state, and exhibits excellent performance as a thin film. Development of a sputtering target that is a thin film manufacturing method and is a raw material thereof is underway.

  In recent years, in order to cope with an improvement in productivity of FPD, etc., the film forming speed during the sputtering process tends to be higher than the conventional one. Increasing the sputtering power is the easiest way to increase the deposition rate. However, increasing the sputtering power causes sputtering defects such as splash (fine molten particles) and defects in the wiring film. As a result, adverse effects such as a decrease in the yield and operating performance of the FPD are brought about.

  Therefore, for the purpose of preventing the occurrence of splash, for example, methods described in Patent Documents 2 to 5 have been proposed. Of these, Patent Documents 2 to 4 are all based on the viewpoint that the cause of the splash is caused by fine voids in the structure of the sputtering target, and Al and rare earth elements in the Al matrix. (Patent Document 2), controlling the dispersion state of a compound of Al and a transition element in an Al matrix (Patent Document 3), adding elements in a sputtering target and Al The occurrence of splash is prevented by controlling the dispersion state of the intermetallic compound (Patent Document 4). In addition, in Patent Document 5, in order to reduce arcing (abnormal discharge) that is a cause of splash, the surface of the surface due to machining is suppressed by adjusting the hardness of the sputter surface and then performing finish machining. A method is disclosed.

  On the other hand, in Patent Document 6, as a technique for preventing the occurrence of splash, an ingot mainly composed of Al is formed into a plate shape by rolling at a processing rate of 75% or less in a temperature range of 300 to 450 ° C., and then at a temperature higher than the rolling temperature. The Vickers hardness of the obtained sputtering target such as an Al—Ti—W alloy is set to 25 or less by performing a heat treatment at 550 ° C. or less and setting the rolled surface side as a sputtering surface.

JP 2004-214606 A Japanese Patent Laid-Open No. 10-147860 JP-A-10-199830 JP 11-293454 A JP 2001-279433 A Japanese Patent Laid-Open No. 9-235666

  As described above, various techniques for reducing the occurrence of splash and improving sputtering defects have been proposed so far, but further improvement is required. In particular, the initial splash generated in the initial stage of sputtering reduces the yield of the FPD, which causes a serious problem. However, the splash generation prevention techniques described in Patent Documents 2 to 5 described above sufficiently generate the initial splash. It cannot be effectively prevented.

  In particular, among Al-based alloys, Al-based alloys that can be applied to the above-described direct contact technology, that is, useful as a wiring material that can be in direct contact with the conductive oxide film constituting the pixel electrode, preferably a photolithography process. It also has excellent corrosion resistance (peeling solution corrosion resistance) against a cleaning solution (typically an organic stripping solution containing amines) that removes the photoresist (resin) formed in step 1. Further, the wiring can be in direct contact with the semiconductor layer of the thin film transistor. Al- (Ni, Co)-(La, Nd) -based alloy applicable as a material, or Al used for forming an Al- (Ni, Co)-(La, Nd)-(Cu, Ge) -based alloy In the base alloy sputtering target, it is desired to provide a technique capable of effectively preventing the occurrence of initial splash even by the conventional melting casting method. That.

  This invention is made | formed in view of the said situation, The objective is an Al- (Ni, Co)-(La, Nd) type alloy or Al- (Ni, Co)-(La, Nd) as a sputtering target. )-(Cu, Ge) It is an object of the present invention to provide a technique capable of reducing the occurrence of splash, particularly initial splash, when an alloy is used.

  The Al-based alloy sputtering target of the present invention that has solved the above problems contains at least one selected from Group A (Ni, Co) and at least one selected from Group B (La, Nd) When the crystal grain size in the rolling direction is measured in a plane parallel to the rolling direction among the cross sections perpendicular to the rolling surface of the sputtering target, the average crystal grain size is 500 μm or less, and the maximum crystal It has a gist where the particle size is 1500 μm or less.

  In a preferred embodiment of the present invention, the total content of Group A is 0.05 atomic% or more and 2.5 atomic% or less, and the total content of Group B is 0.1 atomic% or more and 1 atomic%. It is as follows.

  In a preferred embodiment of the present invention, the Al-based alloy sputtering target further contains at least one selected from Group C (Cu, Ge).

  In preferable embodiment of this invention, the total content of the said C group is 0.1 atomic% or more and 1 atomic% or less.

  In a preferred embodiment of the present invention, the Al-based alloy sputtering target further contains Ti and B.

  In preferable embodiment of this invention, Ti content is 0.0002 atomic% or more and 0.012 atomic% or less, and B content is 0.0002 atomic% or more and 0.012 atomic% or less.

  In a preferred embodiment of the present invention, the Al-based alloy sputtering target is such that only Ni is selected from the A group and only Nd is selected from the B group.

  In a preferred embodiment of the present invention, the Al-based alloy sputtering target is such that only Ni is selected from the A group and only La is selected from the B group.

  In a preferred embodiment of the present invention, the Al-based alloy sputtering target is such that only Ni is selected from the A group, only Nd is selected from the B group, and only Ge is selected from the C group.

  In a preferred embodiment of the present invention, the Al-based alloy sputtering target has a Vickers hardness (Hv) of 26 or more.

  The present invention also includes an Al-based alloy film obtained by using the above sputtering target and directly connected to the transparent conductive film.

  In a preferred embodiment of the present invention, the Al-based alloy film includes at least one selected from Group A (Ni, Co), at least one selected from Group B (La, Nd), and Group C ( Cu, Ge) and at least one selected from Ti and B, the Ti content is 0.0004 atomic% or more and 0.008 atomic% or less, and the B content is 0.0004 atomic%. Thus, the corrosion resistance of the stripping solution is remarkably enhanced.

  According to the present invention, when an Al— (Ni, Co) — (La, Nd) alloy or an Al— (Ni, Co) — (La, Nd) — (Cu, Ge) alloy is used as a sputtering target. In the plane parallel to the rolling direction, the crystal grain size (average crystal grain size and maximum crystal grain size) in the rolling direction is appropriately controlled, so that the occurrence of splash, especially the occurrence of initial splash, can be suppressed, resulting in poor sputtering. Is effectively suppressed.

  In addition, the Al-based alloy film obtained using the sputtering target of the present invention is useful as an Al alloy film for a display device that is in direct contact with the transparent conductive film. In particular, the above-described Al- (Ni, Co)-( An Al-based alloy film obtained by using a sputtering target containing a predetermined Ti and B in a La, Nd) -based alloy or an Al- (Ni, Co)-(La, Nd)-(Cu, Ge) -based alloy is peeled off. Excellent liquid corrosion resistance.

FIG. 3, no. 4 and no. 2 is an optical micrograph showing a crystal grain size of 20. FIG. 2 is a diagram illustrating a Kelvin pattern (TEG pattern) used for measuring the contact resistance between the Al alloy film and the transparent pixel electrode in Example 2.

  The inventors of the present invention have made extensive studies in order to provide an Al-based alloy sputtering target capable of reducing the splash generated during sputtering film formation, particularly the initial splash generated during the initial stage of sputtering film formation. In particular, in the present invention, an Al- (Ni, Co)-(La, Nd) -based alloy or Al- (Ni, Co)-(La, Nd)-(Cu, Ge) -based that can be applied to the direct contact technique described above. Al- (Ni, Co)-(La, Nd) -based alloy sputtering target or Al- (Ni, Co)-(La, Nd)-(Cu, Ge) -based alloy sputtering target, which is useful for alloy film formation In addition, sputtering targets that may further contain Ti and B (hereinafter, these may be collectively referred to as “Al-based alloy sputtering targets”) are used for the above sputtering by a conventional melt casting method. From the viewpoint of providing a technology that can effectively prevent the occurrence of splash even if the target is manufactured.

  As a result, with respect to the Al-based alloy sputtering target, (a) the crystal grain size in the rolling direction (average crystal grain size and maximum crystal grain size) in a plane parallel to the rolling direction among the cross sections perpendicular to the rolling surface. ) Is appropriately controlled, the occurrence of splash is effectively suppressed, and (b) preferably, the occurrence of splash is significantly reduced by increasing the Vickers hardness (Hv) to 26 Hv or more. The headline and the present invention were completed.

In this specification, “the occurrence of initial splash can be prevented (reduced)” means that the average value of splash generated when sputtering is performed under the conditions (sputtering time 81 seconds) shown in the examples described later is 9 to 20. It means a piece / cm ² (evaluation criteria Δ of the example), preferably 8 pieces / cm ² or less (evaluation criteria ○ of the example). As described above, in the present invention, the sputtering time is 81 seconds, and the occurrence of splash in the initial stage is not evaluated in terms of evaluating the splash in the initial stage of sputtering film formation. The evaluation criteria are different from those of this technology.

  First, an Al- (Ni, Co)-(La, Nd) -based alloy or an Al- (Ni, Co)-(La, Nd)-(Cu, Ge) -based alloy that is an object of the present invention will be described.

  First, the Al-based alloy sputtering target of the present invention contains at least one selected from Group A (Ni, Co) and at least one selected from Group B (La, Nd).

  Among them, the group A (Ni, Co) is an element effective for reducing the contact electric resistance between the Al-based alloy film and the pixel electrode that is in direct contact with the Al-based alloy film. It is also useful for controlling the crystal grain size useful for preventing the occurrence of splash. Ni and Co constituting the A group may be used alone or in combination. Of these, Ni is preferred.

  The total content of Group A is preferably 0.05 to 2.5 atomic%. The reason why the total content is 0.05 atomic% or more is to more effectively exert the effect of reducing the contact electric resistance, more preferably 0.07 atomic% or more, and still more preferably 0.1 atomic%. That's it. On the other hand, if the total content of the group A is excessively increased, the electrical resistivity of the Al-based alloy film is increased. More preferably, it is 1.5 atomic%, More preferably, it is 1.3 atomic% or less, More preferably, it is 1.1 atomic% or less.

  Group B (La, Nd) improves the heat resistance of the Al-based alloy film formed using this Al-based alloy sputtering target and prevents hillocks formed on the surface of the Al-based alloy film. It is an effective element. La and Nd constituting the group B may be used alone or in combination.

  The total content of Group B is preferably 0.1 to 1 atomic%. The reason why the total content is 0.1 atomic% or more is to more effectively exhibit the effect of improving heat resistance, that is, the effect of preventing hillocks, more preferably 0.2 atomic% or more, and still more preferably 0. .3 atomic% or more. On the other hand, if the total content of the group C is excessively increased, the electrical resistivity of the Al-based alloy film is increased. More preferably, it is 0.8 atomic% or less, More preferably, it is 0.6 atomic% or less.

  The Al-based alloy used in the present invention contains at least one selected from Group A (Ni, Co) and at least one selected from Group B (La, Nd), and the balance Al and inevitable impurities It is. Inevitable impurities include elements inevitably mixed in the manufacturing process, for example, Fe, Si, C, O, N, etc., and the content of each element is 0.05 atomic% or less. It is preferable.

  Further, the Al-based alloy may contain at least one selected from Group C (Cu, Ge). Group C (Cu, Ge) is an element effective for improving the corrosion resistance of an Al-based alloy film formed using this Al-based alloy sputtering target. Cu and Ge constituting the group C may be used alone or in combination.

  The total content of Group C is preferably 0.1 to 1 atom%. The reason why the total content is 0.1 atomic% or more is to more effectively exhibit the effect of improving the corrosion resistance, more preferably 0.2 atomic% or more, and still more preferably 0.3 atomic% or more. . On the other hand, if the total content of the group C is excessively increased, the electrical resistivity of the Al-based alloy film is increased. More preferably, it is 0.8 atomic% or less, More preferably, it is 0.6 atomic% or less.

  Specific examples of preferred Al-based alloys used in the present invention include, for example, Al-Ni-Nd alloys, Al-Ni-La alloys, Al-Ni-Nd-Ge alloys, Al-Ni-La-Cu alloys, Examples include Al—Co—La—Ge alloys and Al—Co—Nd—Ge alloys.

  Furthermore, the Al-based alloy may contain Ti and B. These are elements that contribute to the refinement of crystal grains, and the addition of Ti and B increases the range of manufacturing conditions (allowable range). However, if it is added excessively, the electrical resistivity of the Al-based alloy film becomes high. The preferable contents of Ti and B are Ti: 0.0002 atom% or more and 0.012 atom% or less, B: 0.0002 atom% or more and 0.012 atom% or less, and more preferably Ti: 0.0004 Atom% or more and 0.006 atom% or less, B: 0.0004 atom% or more and 0.006 atom% or less. Moreover, from the viewpoint of providing an Al-based alloy film having excellent stripping solution corrosion resistance, the preferable contents of Ti and B are both 0.0004 atomic% or more and 0.008 atomic% or less, more preferably 0.001 atomic% or more and 0.006 atomic% or less.

  For addition of Ti and B, a commonly used method can be employed, and typically, addition to the molten metal as an Al—Ti—B refining agent can be mentioned. The composition of Al-Ti-B is not particularly limited as long as a desired Al-based alloy sputtering target can be obtained. For example, Al-5 mass% Ti-1 mass% B, Al-5 mass% Ti -0.2 mass% B or the like is used. These can use a commercial item.

  Next, the crystal grain size of the Al-based alloy sputtering target according to the present invention will be described. In the present invention, when the crystal grain size in the rolling direction is measured in a plane parallel to the rolling direction among the cross sections perpendicular to the rolling surface of the Al-based alloy sputtering target, the average crystal grain size is 500 μm or less, In addition, it is necessary that the maximum crystal grain size satisfies 1500 μm or less. Thereby, generation | occurrence | production of a splash can be prevented effectively.

  The crystal grain size is measured by the intercept method. The specific measurement procedure is as follows.

First, the measurement surface of the Al-based alloy sputtering target (the cross-section perpendicular to the rolling surface is a surface parallel to the rolling direction and within a range of 1/2 × t with respect to the thickness t of the sputtering target). The sputtering target is cut so as to exit. Next, in order to smooth the measurement surface, after polishing with emery paper or diamond paste, Barker's solution (HBF ₄ (tetrafluoroboric acid) and water in a volume ratio of 1:30) Electrolytic etching is performed with a mixed aqueous solution), and the structure is observed with a polarizing microscope. Specifically, the magnification at the time of tissue imaging is 50 times, and two fields of view (one field of view) in a total of three locations on the surface layer side, 1/4 × t part and 1/2 × t part in the thickness direction of the sputtering target. Is taken 1 by 1300 μm long by 1800 μm wide to obtain tissue images. For each tissue image obtained in this way, a straight line corresponding to a total length corresponding to a predetermined length (L1 μm, in the examples described later, the predetermined length L1 is 1800 μm) is parallel to the rolling direction. Randomly draw multiple (about 5-10). Then, the number of crystal grains (N1) that the straight line crosses each texture image is counted, and a value (L1 / N1) obtained by dividing the straight line length (L1 μm) on the image by the number of crystal grains (N1) is obtained. The same operation is performed on the entire measurement visual field, and the average of these is defined as the average crystal grain size (μm). Further, in the entire measurement visual field, the maximum value of the length that the straight line crosses each measurement image is the maximum crystal grain size (μm).

  The average crystal grain size and the maximum crystal grain size of the Al-based alloy sputtering target measured in this way are preferably as small as possible, thereby further reducing the occurrence of splash. A preferred average crystal grain size is 200 μm or less, and a preferred maximum crystal grain size is 800 μm or less. A more preferable average crystal grain size is 150 μm or less, and a more preferable maximum crystal grain size is 500 μm or less.

  The lower limits of the average crystal grain size and the maximum crystal grain size are not particularly limited, but can be determined mainly in relation to the production method. As will be described in detail later, in the present invention, the melt casting method is employed for the purpose of reducing the manufacturing cost, the manufacturing process, and improving the yield. The melt casting method is a method for producing an ingot from an Al alloy molten metal, and is widely used for producing a sputtering target. According to the preferred grain refinement means based on the melt casting method employed in the present invention, the lower limit of the average crystal grain size is about 10 μm to 30 μm, and the lower limit of the maximum crystal grain size is about 70 to 120 μm. is there.

  In order to further refine the crystal grain size, when manufacturing an Al-based alloy sputtering target using the melt casting method, for example, the rolling start temperature is lowered as much as possible, the total rolling reduction is increased as much as possible, or one pass Although it is possible to further reduce the average crystal grain size and the maximum crystal grain size by increasing the rolling reduction as much as possible, it is not practical because there is a possibility that the current equipment cannot be used as it is.

  In addition to the above, the sputtering target production method includes, for example, a spray forming method. By adopting this spray forming method, the crystal grains can be further refined, for example, the average crystal grain size is on the order of several μm. The crystal grains can also be obtained. Here, the spray forming method sprays particles that are sprayed by spraying a high-pressure inert gas into a molten Al alloy flow in a chamber in an inert gas atmosphere, and rapidly cooled to a semi-molten state, a semi-solid state, or a solid state. It is a method of depositing and obtaining a shaped material (preform) having a predetermined shape. However, it has been confirmed by experiments that the effect of suppressing the occurrence of splash is almost the same as that obtained when the spray forming method is used if the means for refining the crystal grain size using the melt casting method employed in the present invention is used. Yes.

  Furthermore, the Al-based alloy sputtering target of the present invention preferably has a Vickers hardness of 26 Hv or more. According to the examination results of the present inventors, an Al— (Ni, Co) — (La, Nd) alloy or an Al— (Ni, Co) — (La, Nd) — (Cu, Ge) system is used as a sputtering target. This is because it has been found that when an alloy is used, initial splash is likely to occur if the hardness of the sputtering target is low. The reason is unknown in detail, but it is assumed as follows. That is, if the sputtering target has a low hardness, the microscopic smoothness of the machined surface by a milling machine or a lathe used for manufacturing the sputtering target is deteriorated. In other words, the material surface is complicatedly deformed. Since it becomes rough, dirt such as cutting oil used for machining is taken in and remains on the surface of the sputtering target. Such dirt is difficult to remove sufficiently even if the surface is cleaned in a later step. As described above, it is considered that the dirt remaining on the surface of the sputtering target is the starting point of the initial splash during sputtering. In order to prevent such dirt from remaining on the surface of the sputtering target, it is necessary to improve workability (sharpness) during machining and prevent the material surface from becoming rough. For this reason, in the present invention, the hardness of the sputtering target is increased.

  The Vickers hardness of the Al-based alloy sputtering target according to the present invention is preferably as high as possible from the viewpoint of preventing the occurrence of splash. For example, it is preferably 35 Hv or more, more preferably 40 or more, and even more preferably 45 or more. It is. The upper limit of the Vickers hardness is not particularly limited, but if it is too high, it is necessary to increase the rolling ratio of cold rolling for adjusting the hardness, and it becomes difficult to perform rolling. Therefore, it is preferably 160 Hv or less, more preferably 140 Hv. Hereinafter, it is more preferably 120 Hv or less.

  Heretofore, the Al-based alloy sputtering target of the present invention has been described.

  Next, a method for producing the Al-based alloy sputtering target will be described.

  As described above, in the present invention, an Al-based alloy sputtering target is manufactured using a melt casting method. In particular, in the present invention, in order to produce an Al-based alloy sputtering target in which the crystal grain size is appropriately controlled, in the process of melt casting → (soaking as necessary) → hot rolling → annealing, hot rolling conditions ( For example, at least one of rolling start temperature, rolling end temperature, 1-pass maximum rolling reduction, total rolling reduction, etc.), soaking conditions (soaking temperature, soaking time, etc.), annealing conditions (annealing temperature, annealing time, etc.) It is preferable to control appropriately. You may perform cold rolling-> annealing (2nd rolling-> annealing process) after the said process.

  Furthermore, in the present invention, preferably, in order to appropriately control the Vickers hardness of the Al-based alloy sputtering target, the hardness can be adjusted by controlling the cold rolling rate in the second rolling → annealing step described above. preferable.

  Strictly speaking, since the crystal grain size refining means and hardness adjusting means that can be applied differ depending on the type of the Al-based alloy, depending on the type of the Al-based alloy, for example, the above-mentioned means may be used alone or in combination. A means may be adopted. Hereinafter, the preferable method used for this invention is demonstrated in detail for every process.

(Melting casting)
The melt casting process is not particularly limited, and a process usually used for manufacturing a sputtering target can be appropriately employed. For example, typical casting methods include DC (semi-continuous) casting, thin plate continuous casting (double roll type, belt caster type, propel type, block caster type, etc.).

(Soaking as needed)
After the ingot of the Al-based alloy ingot as described above, hot rolling is performed, but soaking may be performed as necessary. In order to control the crystal grain size, it is preferable to control the soaking temperature to about 300 to 600 ° C. and the soaking time to about 1 to 8 hours.

(Hot rolling)
After performing the above-mentioned soaking as required, hot rolling is performed. In order to control the grain size, the hot rolling start temperature is about 200 to 500 ° C., the hot rolling end temperature is about 50 to 300 ° C., and the one-pass maximum rolling reduction is about 2 to 25%. It is preferable to control the rate to about 60 to 95%.

  Specifically, for example, when manufacturing an Al—Ni—Nd—Ge alloy sputtering target, for hot rolling, rolling start temperature: 200 to 400 ° C., rolling end temperature: 50 to 200 ° C., one-pass maximum reduction rate : 3 to 25%, total rolling reduction: 70 to 95% is preferable.

(Annealing)
After hot rolling as described above, annealing is performed. In order to control the crystal grain size, it is preferable to control the annealing temperature to about 250 to 450 ° C. and the annealing time to about 1 to 10 hours.

(If necessary, cold rolling → annealing)
Although the crystal grain size of the Al-based alloy sputtering target can be controlled by the above method, cold rolling → annealing (second rolling and annealing) may be further performed thereafter. In order to control the grain size, the cold rolling conditions are not particularly limited, but it is preferable to control the annealing conditions, and the annealing temperature is controlled to about 150 to 250 ° C., and the annealing time is controlled to about 1 to 5 hours. It is recommended.

  Moreover, in order to control the hardness of the Al-based alloy sputtering target, it is preferable to control the cold rolling rate to about 15 to 30%.

  The present invention also includes an Al-based alloy film obtained using the Al-based alloy sputtering target. Such an Al-based alloy film has a low electrical resistivity, and even if it is directly connected to a transparent conductive film (conductive oxide film constituting the pixel electrode), the contact resistance can be kept low. It is suitably used as a wiring film.

  In particular, the Al-based alloy film containing Ti and B is extremely excellent in corrosion resistance to the stripping solution, as demonstrated in Examples described later. Although the TFT substrate manufacturing process passes through a plurality of wet processes, if a metal nobler than Al is included 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 (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.

  As shown in the examples described later, the peel corrosion resistance is changed by the addition of Ti and B. In order to ensure the desired characteristics, the preferable contents of Ti and B are both 0.0004 atomic% or more and 0.008 atomic% or less, and the more preferable contents are both 0.001 atomic% or more. 0.006 atomic% or less.

  The reason why the stripping solution corrosion resistance (corrosion density) changes due to the addition of Ti and B is unknown in detail, but for example, the following mechanisms (1) to (3) are presumed.

  (1) The corrosion starting point in the stripping solution cleaning step is a metal compound of the Al-A group. In the temperature range where the intermetallic compound precipitates, the addition of an appropriate amount of Ti and B causes the crystal growth of the Al alloy film to occur at the same time, so the precipitation site of the intermetallic compound that becomes the origin of corrosion (grain boundary triple point) It is presumed that the corrosion resistance of the stripping solution is improved because the corrosion starting points are dispersed. On the other hand, if the addition amount of Ti and B is insufficient, it is presumed that crystal grain growth occurs before the precipitation of the intermetallic compound, the precipitation sites do not increase, and the stripping solution corrosion resistance does not improve. On the other hand, when the addition amount of Ti and B is excessive, it is presumed that the crystal grain growth of the Al alloy film is conversely suppressed, the precipitation sites are not increased, and the stripping solution corrosion resistance is not improved.

  (2) When Ti and B in the above preferred ranges are added, Ti and B (especially Ti) are not precipitated in the heat history in the manufacturing process of the display device, but are dissolved in the Al alloy film. It is considered that there is a high possibility. In that case, there is an effect of improving the corrosion resistance of the matrix, and it is surmised that the corrosion resistance of the stripping solution is improved by reducing the galvanic corrosion rate with the intermetallic compound.

  (3) Alternatively, an oxide containing Ti and B is formed in the oxide film formed on the surface of the Al alloy film, and the latency time until the stripper comes into contact with the matrix and intermetallic compound in the stripper cleaning process is extended. It can be considered that the corrosion resistance of the stripping solution is improved.

  In order to improve the corrosion resistance against the stripping solution, the method of adding Ti and B as described above is useful. Alternatively, the total content of Group A (Ni, Co) and the total of Group B (La, Nd) The ratio to the content (Group A / Group B) may be controlled to be more than 0.1 and 7 or less. The smaller the ratio, the better. For example, 1.0 or less is preferable, and 0.4 or less is more preferable.

  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 may be implemented with appropriate modifications within a range that can meet the purpose described above and below. These are all possible and are within the scope of the present invention.

Example 1
Various Al-based alloys shown in Table 1 were prepared, and ingots having a thickness of 100 mm were ingoted by the DC casting method, and then hot rolled and annealed under the conditions shown in Table 1 to produce rolled sheets. For reference, the thickness of the produced rolled plate is shown in Table 1.

  Here, an Al-based alloy containing Ti and B was prepared by adding it to the molten metal in the form of an Al-5 mass% Ti-1 mass% B refining agent. For example, in Table 1, No. When producing the Al-based alloy 2 (Ti: 0.0005 atomic%, B: 0.0005 atomic%), the proportion of the above-mentioned micronizing agent is 0.02 mass% with respect to the total mass of the Al-based alloy. On the other hand, no. When the Al-based alloy of No. 3 (Ti: 0.0046 atomic%, B: 0.0051 atomic%) is produced, the proportion of the above-mentioned micronizing agent is 0.2% by mass with respect to the total mass of the Al-based alloy. Added at.

  Further, cold rolling and annealing (200 ° C. for 2 hours) were performed. Here, no. 1 to 3, 5 to 9, and 11 to 25, the cold rolling rate during cold rolling was set to 22%. For 4 and 10, the cold rolling rate was 5%.

  Next, machining (rounding and lathe processing) was performed to manufacture a disk-shaped Al-based alloy sputtering target (size: diameter 101.6 mm × thickness 5.0 mm).

  The crystal grain size (average crystal grain size and maximum crystal grain size) in the rolling direction of each sputtering target thus produced was measured by the above method.

  Furthermore, the Vickers hardness (Hv) of each of the above sputtering targets was measured using a Vickers hardness meter (AVK-G2 manufactured by Akashi Seisakusho Co., Ltd.).

  Next, the number of splashes (initial splash) generated when sputtering was performed using the above sputtering targets under the following conditions was measured.

  First, DC magnetron sputtering was performed on a Si wafer substrate (size: diameter 100.0 mm × thickness 0.50 mm) using a sputtering apparatus of “Sputtering System HSR-542S” manufactured by Shimadzu Corporation. The sputtering conditions are as follows.

Back pressure: 3.0 × 10 ⁻⁶ Torr or less Ar gas pressure: 2.25 × 10 ⁻³ Torr
Ar gas flow rate: 30 sccm, sputtering power: 811 W
Distance between electrodes: 51.6mm
Substrate temperature: room temperature Sputtering time: 81 seconds

  In this way, 16 thin films were formed for each sputtering target. Therefore, sputtering was performed for 81 (seconds) × 16 (sheets) = 1296 seconds.

  Next, using a particle counter (manufactured by Topcon Co., Ltd .: wafer surface inspection device WM-3), the position coordinates, size (average particle diameter), and number of particles observed on the surface of the thin film were measured. Here, particles having a size of 3 μm or more are regarded as particles. Thereafter, the surface of the thin film was observed with an optical microscope (magnification: 1000 times), a hemispherical shape was regarded as a splash, and the number of splashes per unit area was measured.

Specifically, the above-described sputtering process for each thin film is performed in the same manner for 16 thin films while replacing the Si wafer substrate, and the average number of splashes is expressed as “number of occurrences of initial splash”. " In this example, the number of occurrences of the initial splash thus obtained is 8 / cm ² or less, ○, 9 to 20 / cm ² is Δ, 21 / cm ² or more. X was evaluated. In this example, “◯” or “Δ” was evaluated as a pass (with an initial splash reduction effect).

  These test results are also shown in Table 1.

  From Table 1, it can be considered as follows.

First, no. 4 and 10 are examples in which the alloy composition and the crystal grain size in the rolling direction (average crystal grain size and maximum crystal grain size) satisfy the requirements of the present invention, and the number of occurrences of initial splash is 20 pieces / cm ² or less. The initial splash was alleviated.

No. 1-3, 5-9, 11-18 are examples in which the cold rolling rate during the second rolling was appropriately controlled, and in addition to the alloy composition and crystal grain size, the Vickers hardness also satisfies the preferred requirements of the present invention. doing. Therefore, the number of occurrences of initial splash was further suppressed to 8 pieces / cm ² or less, and a further reduction effect of the initial splash was recognized.

  On the other hand, the following examples that do not satisfy any of the requirements of the present invention could not effectively prevent the occurrence of initial splash.

  In detail, first, No. 1 is used. No. 19 is an example in which the amount of Ni is small, both the average crystal grain size and the maximum crystal grain size are large, and the number of occurrences of initial splash is increased.

  No. 20 is an example produced at a temperature higher than the upper limit (400 ° C.) of the hot rolling start temperature recommended when an Al—Ni—Nd—Ge alloy is used, and the average crystal grain size and the maximum crystal grain size Both increased and the number of initial splashes increased.

  No. No. 21 is an example in which the total rolling reduction during hot rolling is less than the lower limit recommended by the present invention (60%), and both the average crystal grain size and the maximum crystal grain size become large, and the initial splash Incidence increased.

  No. 22 is an example in which the hot rolling start temperature was produced at a temperature higher than the upper limit (500 ° C.) recommended in the present invention, both the average crystal grain size and the maximum crystal grain size were increased, and the number of occurrences of initial splash. Rose.

  No. No. 23 is an example in which the one-pass maximum rolling reduction during hot rolling is less than the lower limit (2%) recommended in the present invention, and both the average crystal grain size and the maximum crystal grain size become large. Increased number of splashes.

  No. 24 is an example in which the hot rolling start temperature is produced at a temperature higher than the upper limit (500 ° C.) recommended in the present invention, both the average crystal grain size and the maximum crystal grain size become large, and the number of occurrences of initial splash. Rose.

  No. 25 is an example in which the maximum rolling reduction per pass during hot rolling is less than the lower limit (2%) recommended in the present invention, and the maximum crystal grain size increases and the number of occurrences of initial splash increases. did.

  For reference, FIG. 3 and 4 (invention examples above), and About 20 (comparative example), the optical microscope photograph which shows the crystal grain diameter of a rolling direction is shown. As shown in these photographs, no. In Nos. 3 and 4, the average crystal grain size and the maximum crystal grain size in the rolling direction are controlled to be small. 20, it can be seen that the crystal grain size in the rolling direction is long.

(Example 2)
In this example, the characteristics of an Al-based alloy film obtained using an Al-based alloy sputtering target were evaluated.

  Specifically, various Al-based alloys (remainder: Al and inevitable impurities) shown in Table 2 were prepared, and a sputtering target was manufactured by the method described in Example 1 described above. Here, the hot rolling and annealing conditions are as shown in Table 2, and the cold rolling and annealing conditions are as follows. The sputtering target crystal grain size (average crystal grain size and maximum crystal grain size), Vickers hardness, and number of initial splashes thus obtained were measured in the same manner as in Example 1 described above. The results are also shown in Table 2. In Table 2, No. 1 and no. 4 is No. 4 in Table 1 described above. 2 and no. 3 is supported.

  Using the sputtering target thus obtained, various methods can be used by the DC magnetron sputtering method [substrate = glass substrate (Eagle 2000 manufactured by Corning), atmospheric gas = argon, pressure = 2 mTorr, substrate temperature = 25 ° C. (room temperature)]. An Al alloy film (film thickness = 300 nm) was formed. The content of each alloy element of Ni, Ge, and Nd in the various Al alloy films thus obtained was determined by an ICP emission analysis (inductively coupled plasma emission analysis) method. The result is as shown in Table 2, which is consistent with the composition of the sputtering target used for forming the Al alloy film.

Note that the contents of Ti and B, which are trace element addition elements in the Al alloy film, were as follows after forming five Al alloy films (about 100 mg) at a film thickness of 1000 nm on a 4-inch glass substrate: Each was analyzed by method.
Calculated by ICP emission analysis for Ti content.
The amount of B was calculated by ICP emission analysis or distillation separation-curcumin spectrophotometry according to the amount added.

  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 stripping solution corrosion resistance were measured by the methods shown below.

(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 270 ° C. for 30 minutes or 320 ° C. for 30 minutes, the electrical resistivity was measured by the 4-terminal method.

(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. 2 is prepared by sputtering under the following conditions, and four-terminal measurement (current is 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, by passing a current I between I _{1 and} I ₂ in FIG. 2 and monitoring the voltage V between V _{1 and} V ₂ , the contact resistance R of the contact portion C is set 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)

(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.

More specifically, an amine resist stripping solution (TOK106) manufactured by Tokyo Ohka Kogyo Co., Ltd. was used for the sample obtained by performing the heat treatment (320 ° C. for 30 minutes), and the stripping solution adjusted to (pH = 10.5). The treatment was performed in the order of immersion in an aqueous solution for 1 minute) → (immersion for 5 minutes in an aqueous stripping solution adjusted to pH = 9.5) → (washing with pure water) → (drying). 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)
○: 4.0 or less / 100 μm ²
×: More than 4.0 pieces / 100 μm ²

  These results are summarized in Table 3. Each of Nos. Correspond to each, for example, No. 2 in Table 2. The characteristics of No. 1 are shown in Table 3. As shown in FIG.

  From the results of Tables 2 and 3, it can be considered as follows.

  All the Al-based alloy sputtering targets shown in Table 2 satisfy the requirements of the present invention, and the Al-based alloy film obtained by using such a sputtering target is subjected to heat treatment as shown in Table 3. Therefore, the contact resistance with ITO is kept low, which is useful as a wiring film for direct contact with ITO.

  Of these, No. 2 in Table 2. Nos. 1 to 5 in which Ti and B were not added were those in which the amounts of Ti and B were controlled within a preferable range, such as 1 to 5. 6, No. 2 in Table 2 which does not contain the preferred amounts of Ti and B. It can be seen that compared to 7, the stripping solution is superior in corrosion resistance. The stripping solution corrosion resistance tended to increase as the Ti and B contents increased.

  In Table 2, No. 5 is the ratio of the total content of Group A (Ni, Co) to the total content of Group B (La, Nd) (Group A / Group B = 0.10 / 0.27≈0.37). This is an example satisfying the more preferable range (0.4 or less) of the present invention, and the corrosion density could be suppressed to zero.

Claims (9)

At least one selected from Group A (Ni, Co);
At least one selected from group B (La, Nd) ;
In addition, Ti and B
A sputtering target containing
The total content of Group A is 0.05 atomic% or more and 2.5 atomic% or less,
The total content of Group B is 0.1 atomic% or more and 1 atomic% or less;
Ti content is 0.0002 atomic% or more and 0.012 atomic% or less,
B content is 0.0002 atomic% or more and 0.012 atomic% or less,
Wherein among the cross section perpendicular to the rolling surface of the sputtering target, in the rolling direction and parallel to the plane, when measuring the crystal grain size in the rolling direction, an average grain diameter of. 30 to 500 microns m, and the maximum crystal Al-based alloy sputtering target, wherein the particle sizes of 120~ 1500μ m. The Al-based alloy sputtering target according to claim 1, which is produced by a melt casting method. Furthermore, it contains at least one selected from group C (Cu, Ge) ,
3. The Al-based alloy sputtering target according to claim 1, wherein a total content of the group C is 0.1 atomic% or more and 1 atomic% or less . The Al-based alloy sputtering target according to claim 1 or 2 , wherein only Ni is selected from the A group and only Nd is selected from the B group. The Al-based alloy sputtering target according to claim 1 or 2 , wherein only Ni is selected from the A group and only La is selected from the B group. The Al-based alloy sputtering target according to claim 3 , wherein only Ni is selected from the A group, only Nd is selected from the B group, and only Ge is selected from the C group. The Al-based alloy sputtering target according to any one of claims 1 to 6 , wherein the Vickers hardness (Hv) is 26 or more. An Al-based alloy film obtained using the sputtering target according to any one of claims 1 to 7, directly connected to the transparent conductive film ,
An Al-based alloy film having a Ti content of 0.0004 atomic% to 0.008 atomic% and a B content of 0.0004 atomic% to 0.008 atomic% . A method for producing the sputtering target according to claim 1,
Ingot Al-base alloy ingot by melt casting method,
Hot rolling is performed at a hot rolling start temperature of 200 to 500 ° C., a hot rolling end temperature of 50 to 300 ° C., a one-pass maximum rolling reduction of 2 to 25%, and a total rolling reduction of 60 to 95%.
A method for producing an Al-based alloy sputtering target, comprising performing annealing at 250 to 450 ° C. for 1 to 10 hours after hot rolling.