TW201607914A - Sputtering target - Google Patents

Abstract

This invention provides a sputtering target which has no node formation on the discharging surface of the target during sputtering film formation and particularly during film formation by a DC sputtering method. This invention is a sputtering target which comprises an oxide sintered body comprising Zn, Sn, O and Al, wherein the Al content ratio represented by [(Al mass)/(total mass of the oxide sintered body)*100(%)] is 0.005% to 0.2%, and the Al-containing region displayed in the digital image of the plane analysis result of the discharging surface of the sputtering target by an electron probe microanalyzer is converged in the range of [x]*[y] (x=75 micron, y=75 micron).

Description

Sputter target

The present invention relates to a sputtering target, and more particularly to a sputtering target for an oxide semiconductor film or the like applied to a thin film transistor.

In a display device such as a liquid crystal display or an organic electroluminescence (EL) display driven by a thin film transistor (hereinafter referred to as "TFT"), the channel layer of the TFT is made of amorphous germanium. The filmer has become the mainstream. Further, for example, an oxide semiconductor film containing In (indium), Ga (gallium), Zn (zinc), and O (oxygen) (hereinafter referred to as "IGZO thin film") disclosed in Patent Document 1 has excellent TFT characteristics. And continue to be practical. The In or Ga contained in the IGZO thin film is a rare and expensive metal which is classified as a rare metal reserve target mineral in Japan.

In recent years, an oxide semiconductor film (hereinafter referred to as "ZTO film") containing Zn (zinc), Sn (tin), and O (oxygen) disclosed in Patent Document 2 to Patent Document 4 is not rare and expensive. The In or Ga is constantly receiving attention. When an IGZO thin film or a ZTO thin film is produced by sputtering film formation, an oxide sintered body having a composition substantially equivalent to the component composition necessary for the thin film is usually used for the sputtering target. For example, in the case of producing a ZTO film, a plasma discharge is generated from a sputtering target (hereinafter referred to as a "ZTO target") having a composition necessary for the ZTO film in a mixed gas atmosphere containing argon gas and oxygen gas. The deposit deposited on the film formation surface by the discharge is a ZTO film having a composition substantially equivalent to that of the ZTO target. Similarly, in the production of an IGZO thin film, a sputtering target (hereinafter referred to as "IGZO target") having a component composition necessary for the IGZO thin film is used. [Prior Art Document] [Patent Literature]

[Patent Document 1] Japanese Patent Laid-Open Publication No. Hei. No. Hei. No. Hei. No. Hei. No. Hei. No. Hei. No. Hei. Open 2012-180247

[Problems to be solved by the invention]

The present inventors have found that if Al is contained in a specific range which is not too small in the ZTO film (hereinafter sometimes referred to as "containing a trace amount of Al"), the TFT characteristics can be suppressed when exposed to ultraviolet light or visible light. Deterioration (hereinafter referred to as "light-resistant illuminating property") (International Patent Application No. 2014/060444 to the present inventor). At this time, the ZTO film does not have the desired characteristics.

In the above-described sputtering film formation, a sputtering target which can perform plasma discharge for a long period of time and stably is required. It is considered that a ZTO film which is a deposit of a composition splashed from a ZTO target by plasma discharge has substantially the same or very similar value as a ZTO target prepared in such a manner that the film has desired characteristics. Composition. However, when the composition of the component splashed from the ZTO target is uneven, the composition of the ZTO film is not equivalent to the ZTO target. Further, when the fine particles (fine particles) concentrated by the specific component are splashed and mixed, the composition of the ZTO film is not equal to that of the ZTO target, or structural defects are generated inside the ZTO film.

One of the strong causes of the above problem is a nodule which is generated on the discharge surface of the ZTO target. The nodules are microscopic tumors that are generated by sputtering and film formation on the discharge surface of the sputtering target. When sputtering is continuously formed in a state in which nodules are generated, the frequency of occurrence of abnormal discharge is accelerated, and a film having desired characteristics cannot be obtained. As a means for solving the problem of the nodule or the abnormal discharge, for example, a sputtering target using an oxide sintered body having a Vickers hardness of 400 Hv or more disclosed in Patent Document 4 has been proposed.

However, the inventors of the present invention confirmed that nodules were formed on the discharge surface of the ZTO target having a Vickers hardness of 550 Hv to 600 Hv (see test TG2 described later). Therefore, in order to solve the above problems caused by nodules, it is possible to provide a sputtering target (ZTO target) which is less likely to cause nodules on the discharge surface when sputtering is performed, particularly when sputtering is performed by a DC sputtering method. material). [Means for solving the problem]

The inventors of the present invention studied the sintered structure of the oxide sintered body used for the ZTO target containing a small amount of Al, and clarified the nodules generated on the discharge surface of the ZTO target and the contents existing on the discharge surface. The relationship of the area of Al. Further, it has been found that in the course of conducting research for suppressing the formation of a large Al-containing region, the problem can be solved when the region containing Al is smaller than a specific size.

That is, the present invention is a sputtering target comprising an oxide sintered body containing Zn (zinc), Sn (tin), O (oxygen), and Al (aluminum), and the oxidation In the sintered body of the material, the content ratio of Al expressed by [(mass of Al) / (total mass of oxide sintered body) × 100 (%)] is 0.005% to 0.2%, and the discharge surface of the sputtering target The area containing Al in the digital image of the surface analysis result of the Electron Probe Micro Analyser (hereinafter referred to as "EPMA") converges to [x] × [y] (x = Range of 75 μm, y = 75 μm). Further, the discharge surface of the target before discharge is the surface of the target facing the film formation substrate at the time of sputtering deposition. Further, the discharge surface of the target after discharge is a surface (corrosion surface) of the target which is lost in weight by discharge. Further, in the present invention, it is preferable that the regions containing Al converge in a range of [x] × [y] (x = 50 μm, y = 50 μm).

In the present invention, each range of the Al-containing region displayed in the digital image of the surface analysis result of the electron beam microanalyzer (EPMA) of the sputtering surface of the sputtering target can be evaluated by the following evaluation. obtain.

First, the surface of the sputter target was analyzed by EPMA. The surface analysis analyzes the surface on the side where the sputtering target is discharged when the sputtering is formed. Further, a surface analysis of EPMA using Al as a target was performed on the surface. When the surface analysis of the EPMA to which the Al is targeted is performed, it is carried out under specific analysis conditions. The specific analysis conditions are: Wavelength Dispersive X-ray Spectrometer (WDS), Spectroscopic Crystallization of Thallium Acid Phthalate (TAP), Acceleration Voltage of 15 [kV] The irradiation current was about 5 × 10 ^-7 [A], the beam diameter was f5 [μm] to f25 [μm], and the irradiation time of the beam was 30 [ms]. At this time, the minimum area of the surface analysis is each surface (hereinafter referred to as "unit surface") corresponding to the beam diameter that is irradiated with the beam.

In the present invention, when a digital image (hereinafter sometimes referred to as "EPMA image") of the surface analysis of the EPMA to which Al is targeted is displayed, it is performed under specific display conditions. The specific display condition is the gradation displayed by the brightness of 16 gray scales. The size (interval) of the pixels is 5 μm × 5 μm or 25 μm × 25 μm corresponding to the beam diameter. The maximum value of gray scale is 2000. At this time, since the full scale (16 gray scale) is 2000, the unit scale (unit gray scale) is 125 steps.

For example, when the pixel of the EPMA image is displayed in black of 0 to 125 (less than 125) (first gray scale), the content ratio of Al of the unit surface corresponding to the pixel is 0% or It is roughly 0%. Further, the content ratio of Al on the unit surface corresponding to the pixel of 125 to 250 (125 or more and less than 250) (second gray scale) is larger than the unit surface corresponding to the pixel of the first gray scale. Therefore, the display of pixels is in the order of 250 to 375 (250 or more and less than 375) (third gray scale), 375 to 500 (375 or more and less than 500) (fourth gray scale), ... (middle omitted)... The 1875 to 2000 (1875 or more) level (sixteenth gray scale) is brightened, and the content ratio of Al per unit surface corresponding to the pixel is increased. In addition, the threshold values of the two adjacent gray scales (for example, the threshold value of the first gray scale and the second gray scale is 125) belong to which of the two gray scales, and vary according to the image display program.

The Al-containing region corresponds to a pixel represented by a second grayscale to a sixteenth grayscale (125th to 2000th grade) in the EPMA image. Further, a region in which the pixels of the second gray scale or higher are separated or continuous is a region containing Al. Here, in the case of a single pixel, if it is contacted by a side or an angle, it is continuous, and the aggregate of the continuous pixels is a region containing Al. For example, when the display is as shown in FIG. 1 in which all the sides and corners of one pixel above the second gray level are adjacent to the pixels of the first gray level, in the dotted circle in the figure above the second gray level A pixel corresponds to a region containing Al. At this time, if the size of the pixel is 5 μm × 5 μm, then x = pixel number (one) × pixel size (5 μm) and y = pixel number (one) × pixel size (5 Μm), so the range defined as the region containing Al converges to [x] × [y] (x = y = 5 μm).

In addition, when the three pixels above the second gray level are displayed adjacent to each other in FIG. 2, the three pixels above the second gray level are added to one pixel of the first gray level. The four pixels in the dotted circle in the figure correspond to the area containing Al. At this time, since the number of pixels is 2 × 2, if the size of the pixel is 5 μm × 5 μm, the range defined as the region containing Al converges to [x] × [y] (x = 10 μm, y =10 μm).

In addition, when the display is as shown in FIG. 3 adjacent to two pixels above the second gray level adjacent to the angle, the two pixels above the second gray level plus the two pictures of the first gray level The four pixels in the dotted circle in the obtained graph correspond to the region containing Al. At this time, since the number of pixels is 2 × 2, if the size of the pixel is 5 μm × 5 μm, the range defined as the region containing Al converges to [x] × [y] (x = 10 μm, y =10 μm).

If it is referred to in the same manner, in the display shown in FIG. 4, the six pixels above the adjacent second gray level on the left side, the five pixels above the second gray level adjacent to the right side, and the left side will be left. The pixel group and the right pixel group are connected in a manner of a pixel above the second gray level adjacent to the center, plus two paintings of the first gray level adjacent to the upper and lower sides of the central pixel The fifteen pixels in the dashed circle in the figure obtained by one pixel of the first gray scale adjacent to the lower right pixel group of the right side correspond to the region containing Al. At this time, since the number of pixels is 5 × 3, if the size of the pixel is 5 μm × 5 μm, the range defined as the region containing Al converges to [x] × [y] (x = 25 μm, y =15 μm).

In addition, in the display shown in FIG. 5, since the pixel group on the left side and the pixel group on the right side are not adjacent, there is an area containing Al corresponding to six pixels in the dotted circle on the left side in the figure. (A) and a region (B) containing Al corresponding to six pixels in the dotted circle on the right side in the figure. At this time, if the size of the pixel is 5 μm × 5 μm, both the region containing Al (A) and the region containing Al (B) converge to [x] × [y] (x = 10 μm, y = 15). The range of μm). [Effects of the Invention]

In the sputtering target (ZTO target) of the present invention, when a film is formed by sputtering, particularly when a film is formed by a DC sputtering method, no agglomeration is likely to occur, and thus abnormal discharge due to nodules and splashing of fine particles are hard to occur. Therefore, by using the ZTO target as the embodiment of the present invention, it is possible to prevent unevenness in the composition of the sputter deposit due to nodules and the incorporation of fine particles into the sputter deposit, and it is possible to obtain desired ZTO film of various characteristics.

The sputtering target (ZTO target) of the present invention is a ZTO target using an oxide sintered body containing Zn, Sn, and O (hereinafter referred to as "ZTO sintered body"). A small amount of Al is contained in the ZTO sintered body used for the ZTO target, and the content ratio of Al expressed by [(mass of Al) / (total mass of oxide sintered body) × 100 (%)] is 0.005% to 0.2%. . From the viewpoint of material cost, ZTO targets are advantageous over IGZO targets because they use ZTO sintered bodies that do not contain rare and expensive In or Ga.

A ZTO target having a content ratio of Al of the above range (0.005% to 0.2%) can realize control of a carrier, and a ZTO film having optical stress resistance can be sputter-deposited. It has been found that a ZTO film having optical stress resistance can suppress degradation of characteristics after exposure to ultraviolet light or visible light, for example, variation of Vg-Id characteristics of gate voltage (Vg) and gate current (Id) can be suppressed. Small level (International Patent Application No. 2014/060444 according to the present inventors). At this time, the ZTO film is effectively used for the practical use of a high-quality and high-characteristic TFT equivalent to or higher than that of the IGZO film. From the viewpoint of suppressing the change in the Vg-Id characteristics, Al may be from 0.008% by mass to 0.1% by mass, or may be from 0.008% by mass to 0.05% by mass.

The ZTO sintered body of the present invention has a matrix phase containing Zn-containing Zn oxide (ZnO or the like), Sn-containing Sn oxide (SnO ₂ or the like), and Zn and Sn-containing ZnSn composite oxide. (Zn ₂ SnO _{4 ,} etc.). Further, it has a region containing Al containing Al in such a manner as to be dispersed in the matrix phase. When a ZTO film having a composition substantially equivalent to that of the ZTO target is obtained, a ZTO sintered body having a small Al-containing region of the matrix phase dispersed in the ZTO sintered body can be used. Further, it is more preferable if the dispersed state of the small Al-containing region is uniform.

The region containing Al is a region containing Al, and contains, for example, an Al oxide (Al ₂ O ₃ or the like), which is harder than the oxide constituting the matrix phase. When a discharge occurs at the time of sputtering, the constituent material of the target splashes from the discharge surface of the target. At this time, the soft matrix phase is preferentially consumed, and as a result, the hard Al-containing region becomes a nodule and appears on the discharge surface of the target. Even if it is a nodule, when it is a large nodule, it also affects the performance of the ZTO film. In addition, even if each of the nodules is a fine tumor, when the fine tumors are locally aggregated and have a large tumor shape, the performance of the ZTO film may be affected. That is, when a hard Al-containing region appears on the discharge surface of the target, if it is a large nodule or has a large tumor shape, it becomes harmful to the performance of the ZTO film. Nodule.

Therefore, the Al-containing region of the matrix phase of the ZTO sintered body, that is, the region containing each of Al and the Al-containing region which is locally aggregated and has a form such as one region is preferably finer. Specifically, the range of each Al-containing region in the discharge surface of the ZTO target displayed in the EPMA image preferably converges to [x]×[y] (x=75 μm, y=75 μm). . The ZTO target having the above configuration can suppress the occurrence of nodules on the discharge surface of the target. Further, from a finer viewpoint, the range of the Al-containing region displayed in the EPMA image preferably converges to [x] × [y] (x = 50 μm, y = 50 μm).

The ZTO sintered body may contain 50% by mass or more of an oxide containing Zn (ZnO or the like), an oxide containing Sn (SnO ₂ , etc.), based on the mass ratio of the total amount of the oxide sintered body. And a ZnSn composite oxide (Zn ₂ SnO ₄ or the like) containing Zn and Sn. Here, "the oxide containing Zn and the oxide containing Sn are 50% by mass or more in total" means that the oxide sintered body contains an oxide containing Zn and an oxide containing Sn. A ZTO film having a high content ratio of ZnO or the like containing Zn is known to have excellent etching resistance. Therefore, by using a ZTO target obtained by using a sintered body containing a high content of an oxide containing Zn, a ZTO film having particularly high etching resistance than the IGZO film can be obtained.

Further, a ZTO film having a specific ratio of Zn to Sn is known, and it is known that the mobility of the carrier in the TFT can be favorably maintained. Therefore, in the ZTO sintered body, the ratio of Zn (hereinafter referred to as "z value") expressed by [Zn/(Zn+Sn) × 100 (%)] with respect to the total amount of Zn and Sn is referred to as an atom. The ratio meter is preferably more than 52% and less than 80%. By the z value of 80% or less, the mobility of the carrier of the ZTO film can be favorably maintained. Further, the z value is in the range of more than 52%, and the resistance to the etching liquid is not excessively strong, and the etching property when the ZTO film is formed into a desired pattern is further improved. In other words, by setting the z value to be in the range of more than 52% and 80% or less, the balance between the easiness of etching of the ZTO film and the carrier mobility is good. The range of z values is preferably from 59% to 70%.

The ZTO sintered body may further contain other elements than Zn, Sn, O, and Al as long as it is a trace amount. As said trace element, Si (矽) is mentioned, for example. In the ZTO sintered body, the content ratio of Al and Si expressed by [(the mass of Al + mass of Si) / the total mass of the oxide sintered body × 100 (%)] is 0.1% or less Si exceeding the range of the content of Al, and the sintered density (relative density) is improved.

In addition, for example, Ga (gallium), In (indium), W (tungsten), Ta (钽), Hf (铪), and Nb (铌) are considered to have an effect of exhibiting the same tendency as Al. ), Cr (chromium), B (boron), V (vanadium), and Fe (iron), or Ge (锗), Pb (lead), As (arsenic), which are considered to have the same tendency as Si. Sb (锑), Bi (铋). Further, the trace elements which are easily mixed in from the raw material or the production step include C (carbon), S (sulfur), P (phosphorus), N (nitrogen), and H (except for Fe, Pb, and Sb). Hydrogen), Mg (magnesium), Zr (zirconium), Mn (manganese), Cd (cadmium). Other elements (including Si) other than Zn, Sn, O, and Al are preferably suppressed in a range of less than 0.03 mass% with respect to the total mass of the ZTO sintered body. Further, the other elements are preferably suppressed in a range not exceeding the content of Al.

The Vickers hardness in the discharge surface of the ZTO target using the ZTO sintered body may be 300 Hv or more, more preferably 400 Hv or more and even 500 Hv or more. Corresponding to this, the sintered density (relative density) of the ZTO sintered body may be 92% or more, more preferably 93% or more and even 95% or more. The Vickers hardness can be obtained from the cross-sectional area of the depression formed by pressing the diamond indenter of the quadrangular pyramid in the test piece as defined in JIS-Z2244 (2009).

In the technical field of the present invention, the smaller the volume resistivity of the ZTO target, which is also referred to as the resistivity, the better. In particular, the volume resistivity is preferably 0.10 [Ω·cm] from the viewpoint of DC discharge stability at the time of film formation by a DC sputtering method (for example, direct current (DC) magnetron sputtering method). ]the following. [Examples]

Hereinafter, embodiments of the sputtering target (ZTO target) of the present invention will be more specifically described by way of examples and comparative examples. However, the present invention is not limited to the following embodiments as long as it does not deviate from the gist thereof.

(Production of ZTO Target) When producing a ZTO target containing a small amount of Al, it is preferable to mix an oxide raw material containing Al or Al and Zn in an oxide raw material containing Zn and an oxide raw material containing Sn. Oxide raw material. In such a production method, the Al-containing region contained in the ZTO sintered body may not be uniform depending on a series of manufacturing processes such as mixing or kneading of an oxide raw material or the like, subsequent molding or sintering, or the like. It exists in various sizes or forms. Paying attention to such a viewpoint, the inventors made a ZTO target.

First, a powder raw material is prepared. A high-purity powder containing substantially no trace elements such as Al or Si, a zinc oxide powder containing Zn (hereinafter referred to as "ZnO powder"), and a tin oxide powder (IV) containing Sn (hereinafter referred to as "SnO ₂ powder" are prepared. """. Further, an Al-containing zinc oxide powder (hereinafter referred to as "AZO powder") containing a specific amount of Al in Zn is prepared.

The ZnO powder and the SnO ₂ powder were mixed and kneaded sufficiently to prepare a mixed powder of ZnO powder and SnO ₂ powder. Then, the mixed powder is mixed with the AZO powder, kneaded sufficiently, and then a binder or the like is mixed, and further kneaded to further prepare a first molding powder containing Zn, Sn, O, and Al. At this time, the blending amount of the AZO powder was adjusted so as to have a content ratio of Al of 0.1% by mass based on the total mass of the oxide sintered body. Finally, the blending amount of the ZnO powder and the SnO ₂ powder contained in the first molding powder was z = 0.7 in the case of the oxide sintered body [(ZnO)z(SnO ₂ )1-z]. Then, the molded body is molded by using the first molding powder, and the powder is sintered by removing a binder or the like from the molded body to produce a first plurality of ZTO sintered bodies. Then, the first plurality of ZTO sintered bodies are processed into a specific shape to obtain a first ZTO target having a discharge surface (hereinafter referred to as "test TG1").

Then, the ZnO powder, the SnO ₂ powder, and the AZO powder which are the same as the test TG1 are simultaneously mixed, kneaded sufficiently, and then a binder or the like is mixed, and further kneaded to further form a second shape including Zn, Sn, O, and Al. Use powder. In this case, in the same manner as in the test TG1, each powder was adjusted so that the ZnO powder and the SnO ₂ powder contained in the second molding powder were in a molar ratio of x=0.7 and Al of 0.1% by mass. The amount of blending. Then, the molded body is molded by using the second molding powder, and the powder is sintered by removing the binder or the like from the molded body to produce a second plurality of ZTO sintered bodies. Then, the second plurality of ZTO sintered bodies were processed into the same shape as the test TG1 to obtain a second ZTO target having a discharge surface (hereinafter referred to as "test TG2").

The sintered density (relative density) of the test TG1 and the test TG2, which are ZTO targets produced in the manner described above, was measured. The sintered density was 93.7% for the test TG1 and 96.4% for the test TG2. Further, the Vickers hardness of the discharge surface (before discharge) of the test TG1 and the test TG2 was measured. The Vickers hardness is 350 Hv to 400 Hv for the test TG1 and 550 Hv to 600 Hv for the test TG2.

Then, a sputtering film formation test was performed using the test TG1 and the test TG2. At this time, the discharge faces of the test TG1 and the test TG2 were observed by a metal microscope before sputtering (before discharge) and after sputtering (after discharge). (Discharge surface of test TG1) The discharge surface before the sputtering (before discharge) of the test TG1 shown in Fig. 6 has a processing mark in the oblique direction in the drawing, and other abnormal forms are not particularly observed. The discharge surface after the sputtering (after discharge) of the test TG1 shown in FIG. 7 has a uniform rough surface in which the processing marks before discharge disappear. Further, no nodule or other abnormality was observed on the discharge surface after the sputtering (after discharge) of the test TG1. According to the results, it was found that the test TG1 in which the discharge surface was uniformly roughened after the sputtering was excellent in discharge stability at the time of sputtering.

(Explosion surface of test TG2) The discharge surface before the sputtering (before discharge) of the test TG2 shown in Fig. 8 had a small amount of processing marks in the oblique direction in the drawing, and a pattern as seen as a black spot was observed. The discharge surface after the sputtering (after discharge) of the test TG2 shown in FIG. 9 has a rough surface in which the processing marks before discharge disappear. Further, in the discharge surface after the sputtering (after discharge) of the test TG2, a large number of patterns having a size such as a white portion having a central portion and a black surrounding were observed. According to such a result, the pattern which was generated on the discharge surface of the test TG2 and which did not appear in the test TG1 was presumed to be a nodule due to the presence of a large Al-containing region. Therefore, it is considered that the test TG2 has a poor discharge stability at the time of sputtering film formation as compared with the test TG1.

(Sintered structure of test TG1 and test TG2) The discharge surface (before discharge) of test TG1 and test TG2 was observed by surface analysis of EPMA. EPMA used a JXA-8900R WD/ED combined microanalyzer (COMBINED MICROANALYZER) manufactured by JEOL. The analysis conditions of the face analysis are the specific analysis conditions. The beam diameter was f5 μm at the time of test TG1 and f25 μm at the time of test TG2.

The Zn distribution, the Sn distribution, the O (oxygen) distribution, and the Al distribution of a part of the discharge surface of the test TG1 are shown in FIGS. 10, 11, 12, and 13 in the same field of view of the EPMA surface analysis. Similarly, a digital image of the same field of view of the Zn distribution, the Sn distribution, the O (oxygen) distribution, and the Al distribution of the discharge surface of the test TG2 in the surface analysis of the EPMA is shown in FIG. 14, FIG. 15, FIG. 16, and FIG. . Here, in order to more clearly show the dispersion state of Al in the discharge surface of the test TG1 and the test TG2, the maximum value of the gradation of the display of the Al distribution is 400. Further, the magnification of the display of the digital image of FIGS. 14 to 17 is about 3.4 times as shown in FIGS. 10 to 13 .

It is understood that the sintered structure of the test TG1 has a matrix phase in which Zn, Sn, and O are substantially uniformly dispersed. For example, after observing FIG. 10, the area where Zn is a medium-density gray is enlarged. The gray area is the tissue where Zn coexists with other elements. A small dot indicating that Zn is a high concentration of white is enlarged in a manner of forming a mesh pattern in the gray structure. The small dots of white are also distributed on the inner side of the mesh pattern. A small black dot indicating that Zn is a low concentration is distributed as a network pattern formed by white dots. Further, when compared with FIG. 10, FIG. 11, and FIG. 12, it is understood that Sn, O, and Zn are distributed in substantially the same form. Further, when compared with FIG. 10 and FIG. 13, it is understood that Al is distributed along the mesh of the mesh pattern of Zn.

It was found that the sintered structure of the test TG2 had a matrix phase in which Zn, Sn, and O of the same form as the test TG1 were substantially uniformly dispersed. However, in the test TG2 in which nodules were formed on the discharge surface, a significant difference was found in the form of Al distribution. In the test TG1 (Fig. 13), the small dots of white were substantially uniformly dispersed, but in the test TG2 (Fig. 17), a large number of dots of white were found. A considerable number of dots of white indicate that Al is at a high concentration. For example, in the region in FIG. 15 corresponding to the region from the center to the upper right of the large dot of white in FIG. 17, there is a large dot indicating that Sn is a low density or a lack of Sn. In the region in Fig. 16 corresponding to the region in Fig. 17, there is a large dot indicating that O is a high concentration of white. The positions of the large white dots of Al, the large black dots of Sn, and the large white dots of O are sufficiently matched. From the results, it is understood that the large white point of Al is a region containing Al containing an oxide of Al (such as Al ₂ O ₃ ).

(Testing TG1 and Region Containing Al in Test TG2) The region containing Al on the discharge surface (before discharge) of Test TG1 and Test TG2 will be described. The Al distribution of the discharge surfaces of the test TG1 and the test TG2 is shown in Figs. 18 and 20 . In addition, an enlarged view of a part of FIGS. 18 and 20 is shown in FIGS. 19 and 21. The display condition of the digital image of the face analysis is the specific display condition. The size of the pixel corresponding to the beam diameter of the surface analysis was 5 μm × 5 μm in the test TG1 and 25 μm × 25 μm in the test TG2. The maximum value of the gradation which is divided into sixteen gray scales from the first gray scale to the sixteenth gray scale by the luminance meter is 2000.

In the test TG1 (Fig. 18), three white regions in which Al is highly concentrated, that is, a region containing Al, were found slightly above the center in the figure. In addition, several small gray dots were also found. The portion including the three white regions in Fig. 18 is enlarged and shown in Fig. 19. Regarding the three Al-containing regions 10, the Al-containing regions 11, and the Al-containing regions 12 in Fig. 19, the number of pixels is 2 × 3, 2 × 3, and 3 × 3, respectively. At this time, since the size of the pixel is 5 μm × 5 μm, the range of the region 10 containing Al, the region 11 containing Al, and the region 12 containing Al converges to [x] × [y] (x = 10 μm, respectively). , y = 15 μm), [x] × [y] (x = 10 μm, y = 15 μm) and [x] × [y] (x = 15 μm, y = 15 μm). Therefore, the Al-containing region 10 of the test TG1, the Al-containing region 11, and the Al-containing region 12 converge to the [x]×[y] (x=75 μm, y=75 μm) which the inventors prescribed to suppress the occurrence of nodules. ).

In the test TG2 (Fig. 20), three white regions in which Al is a high concentration, that is, a region containing Al, were found in three places in the figure. A portion including the region of the largest white at the lower left in FIG. 20 is enlarged and shown in FIG. 21. The number of pixels of the region 13 containing Al in Fig. 21 is 5 × 5. At this time, since the size of the pixel is 25 μm × 25 μm, the range of the region 13 containing Al is expanded to [x] × [y] (x = 125 μm, y = 125 μm). Therefore, it is understood that the Al-containing region 13 of the test TG2 in which nodules are formed on the discharge surface does not converge to [x] × [y] (x = 75 μm, y = 75 μm). [Industrial availability]

A sputtering target (ZTO target) as an embodiment of the present invention can be used as a sputtering target for sputtering an oxide semiconductor film (ZTO film) into a film.

10 to 13‧‧‧ Areas containing Al

Fig. 1 is a schematic view showing a display form of an EPMA image corresponding to a region containing Al. 2 is a schematic diagram showing a display form of an EPMA image corresponding to a range of four pixels and a region containing Al. 3 is a schematic diagram showing a display form of an EPMA image corresponding to a range of four pixels and a region containing Al. 4 is a schematic diagram showing a display form of an EPMA image corresponding to a region containing fifteen pixels and a region containing Al. Fig. 5 is a view showing a display form of an EPMA image in which two regions (A) containing Al and regions (B) containing Al exist in a range containing fifteen pixels. Fig. 6 is a view (photograph) showing a part of the discharge surface before the discharge of the test TG1. Fig. 7 is a view (photograph) showing a part of the discharge surface after the discharge of the test TG1. Fig. 8 is a view (photograph) showing a part of the discharge surface before the discharge of the test TG2. Fig. 9 is a view (photograph) showing a part of the discharge surface after the discharge of the test TG2. Fig. 10 is a view showing a Zn distribution of a part of the discharge surface of the test TG1 (before discharge) (a digital image of the surface analysis of EPMA). Fig. 11 is a view showing a distribution of Sn of a part of the discharge surface of test TG1 (before discharge) (a digital image of the surface analysis of EPMA). Fig. 12 is a view showing a distribution of O (oxygen) of a part of the discharge surface of test TG1 (before discharge) (a digital image of the surface analysis of EPMA). Fig. 13 is a view showing a distribution of Al in a part of the discharge surface of the test TG1 (before discharge) (a digital image of the surface analysis of EPMA). Fig. 14 is a view showing a Zn distribution of a part of the discharge surface of test TG2 (before discharge) (a digital image of the surface analysis of EPMA). Fig. 15 is a view showing a distribution of Sn of a part of the discharge surface of the test TG2 (before discharge) (a digital image of the surface analysis of EPMA). Fig. 16 is a view showing a distribution of O (oxygen) of a part of the discharge surface of test TG2 (before discharge) (a digital image of the surface analysis of EPMA). Fig. 17 is a view showing a distribution of Al in a part of the discharge surface of test TG2 (before discharge) (a digital image of the surface analysis of EPMA). Fig. 18 is a diagram showing the Al distribution of a part of the discharge surface of the test TG1 (before discharge) under a specific display condition (a digital image of the surface analysis of EPMA). Fig. 19 is a view showing a region containing Al existing in the Al distribution shown in Fig. 18 and showing it under specific display conditions (a digital image of the surface analysis of EPMA). Fig. 20 is a graph showing the Al distribution of a part of the discharge surface of the test TG2 (before discharge) under a specific display condition (a digital image of the surface analysis of EPMA). Fig. 21 is a view showing a region containing Al existing in the Al distribution shown in Fig. 20 and showing it under specific display conditions (a digital image of the surface analysis of EPMA).

Claims (2)

A sputtering target comprising an oxide sintered body containing Zn, Sn, O, and Al, and in the oxide sintered body, [(Al mass) / (oxide sintering) The total content of the body × 100 (%)] indicates a content ratio of Al of 0.005% to 0.2%, and a digital map of the surface analysis result of the electron beam microanalyzer (EPMA) of the discharge surface of the sputtering target The region containing Al shown in the image converges in the range of [x] × [y] (x = 75 μm, y = 75 μm). The sputtering target according to claim 1, wherein the region containing Al converges in a range of [x] × [y] (x = 50 μm, y = 50 μm).