WO2001034869A1

WO2001034869A1 - Sputtering target and method for preparation thereof

Info

Publication number: WO2001034869A1
Application number: PCT/JP2000/005172
Authority: WO
Inventors: Keiichi Ishizuka
Original assignee: Nikko Materials Company, Limited
Priority date: 1999-11-09
Filing date: 2000-08-02
Publication date: 2001-05-17
Also published as: JP3628566B2; TWI225521B; KR100413958B1; JP2001131736A; KR20010093248A

Abstract

A sputtering target comprising an indium-zinc based oxide (IZO sputtering target), characterized as having a structure of two phases, one being an indium-rich phase comprising indium oxide crystals and Zn dissolved or not dissolved therein, and the other being a zinc-rich phase comprising zinc oxide crystals and In dissolved or not dissolved therein. The sputtering target exhibits some improved properties while maintaining excellent characteristics inherent to an IZO transparent conductive film comprising an indium-zinc based oxide as a main component. The increase of density, the minimization and/or homogenization of crystal grains and the enhancement of deflection strength, with respect to the above target, lead to the stabilization of the discharge during sputtering and to the production of a transparent conductive film with stability and with good reproducibility.

Description

Description Sputtering target and method for producing the same

The present invention relates to an Izo sputtering target suitable for forming a transparent conductive film containing indium and zinc oxide as a main component, which has a fine crystal structure, a high sintered body density, and a high transverse rupture strength, and its production. About the method. Background art

Transparent conductive films made of several metal composite oxides have high conductivity and visible light transmission, so liquid crystal displays, thin film electroluminescent displays, radiation detectors, transparent tablets for terminal equipment, It is used in a wide variety of applications, such as heat generating films for preventing dew condensation on window glass, antistatic films or permselective films for solar collectors, and electrodes for touch panels.

The most popular of the transparent conductive films made of such a metal composite oxide is a transparent conductive film made of thidium indium indium tin, which is called I τ〇.

In addition, tin oxide to which antimony (Α Τ に) is added or zinc oxide to which aluminum (Α Ζ Ο) is added is known. These differ from each other in terms of film characteristics and manufacturing costs, so they are used as appropriate according to the application.

Among them, a proposal has been made to use a transparent conductive film mainly composed of a complex oxide of indium and zinc (hereinafter referred to as “IZO” unless otherwise specified) having a higher etching rate than that of an ITO film (Patent No. No. 2,695,605).

The IZO target used for the film formation at this time was manufactured by a hot isostatic pressing method (see Examples 4 to 12 of the above-mentioned Patent Publication). However, the conventional IZO sputtering target manufactured by this method did not have a sufficiently high sintering density, and had a non-uniform crystal grain size. In addition, the obtained target did not have sufficiently low Balta resistance, and was not necessarily the optimal sputtering target for DC sputtering.

Furthermore, since the mechanical strength of the sintered target by the hot isostatic pressing method is low, there is a problem that chipping or cracking occurs during sputtering or during handling of the target. Disclosure of the invention

In view of the above, it is an object of the present invention to improve the properties of an IZO transparent conductive film containing indium and zinc oxides as main components without losing the properties, improve the target density, and improve the crystal grain size. Provided is an IZO sputtering target capable of uniformly miniaturizing and improving mechanical properties, stabilizing sputtering discharge, and obtaining a stable and reproducible transparent conductive film, and a method for producing the same.

The present invention is based on the following two aspects: 1) an In-rich phase in which Zn is dissolved or insoluble in indium oxide crystals; A sputtering target composed of an indium-zinc-based oxide characterized by having a phase structure.2) The average diameter of the Zn atom aggregates observed by EPMA is 10 μππι or less. The sputtering target comprising the zinc oxide dumbbell-based oxide as described in 1 above, 3) the average diameter of aggregates of ηη atoms observed in Ε Ε is 5 m or less. 4. A sputtering target comprising the indium zinc-based oxide described in 1), 4) a sintered zinc-based oxide according to any one of the above items 1 to 3, wherein the sintered body density is 6.5 g / cm ³ or more. Target), 5) average crystal A sputtering target comprising the zinc oxide based oxide according to any one of the above items 1 to 4, wherein the particle diameter is 3 m or less; 6) The sputtering target comprising an indium-zinc oxide according to any of 1 to 5 above, wherein the average crystal grain size is 2 μm or less.7) The surface roughness is 2 m at Ra. Hereinafter, the sputtering target comprising the zinc oxide according to any one of the above items 1 to 6, characterized in that the average transverse rupture strength is 68 MPa or more.8) The surface roughness is 0. The sputtering target comprising an indium-zinc-based oxide according to any one of 1 to 6 above, wherein the sputtering target is 5 μm or less, and the average bending strength is 78 MPa or more.9) Indium-dumbbell-based oxide Each of the above items 1 to 8, wherein Fe, Al, Si, Ni, Ti, and Cu, which are impurities in the sintered body, are each less than or equal to 10 ppm (wt). Sputtering target composed of indium zinc oxide, 10) acid After finely pulverizing indium and zinc oxide, they are mixed and granulated, molded by cold pressing and / or isostatic pressing, and then heated to 130 to 150 ° C in an oxygen atmosphere or air. It is characterized by sintering; Zn rich solid phase or non-solid solid phase in zinc oxide crystal and Zn rich solid phase with zinc solid solution or non-solid solution in zinc oxide crystal Method for manufacturing sputtering target composed of zinc-zinc oxide having two-phase structure of 1) 1) The diameter of aggregate of Zn atoms observed by E PMA is 10 m or less The method for producing a sputtering target comprising an indium-zinc oxide according to the item 10, wherein the sintered body has a density of 6.5 g Z cm ³ or more. Or a sputtering target comprising the indium-zinc oxide according to 11 Production method, 13) A method for producing a sputtering target comprising an indium monosuboxide as described in each of the above items 10 to 12, wherein the average crystal grain size is 3 μm or less. 4) The method for producing a sputtering target comprising an indium-monous zinc-based oxide as described in each of the above items 10 to 12, wherein the average crystal grain size is 2 m or less; 15) Surface roughness A sputtering target comprising an indium-zinc-based oxide according to any one of the above 10 to 14, characterized in that the Ra is 2 / xm or less in Ra and the average bending strength is 68 MPa or more. Manufacturing method, 16) The sputtering target comprising an indium-zinc-based oxide as described in each of 10 to 15 above, wherein the surface roughness is 0 or less in Ra and the average bending strength is 78 MPa or more. Manufacture method, 17) Fe, Al, Si, Ni, Ti, and Cu, which are impurities in the indium-zinc oxide sintered body, are each less than 10 ppm (wt). And a method for producing a sputtering target comprising an indium-zinc-based oxide according to any of the above items 10 to 16. BRIEF DESCRIPTION OF THE FIGURES

FIG. 1 is a diagram showing the results of qualitative analysis of indium by EPMA on the surface of an IZO target material of the present invention.

FIG. 2 is a view showing the results of qualitative analysis of zinc by EPMA on the surface of the IZO target material of the present invention.

FIG. 3 is a diagram showing the results of qualitative analysis of oxygen by EPMA on the surface of an IZO target material of the present invention.

FIG. 4 is a diagram showing the cumulative fracture probability with respect to the bending strength of the IZO target of the present invention.

FIG. 5 is a diagram showing the same Weibull plot of the IZO target of the present invention. Embodiment of the Invention

In the production of a sputtering target containing an acid substance of indium and zinc as a main component, for example, zinc oxide powder having the same particle diameter as powder of indium oxide having an average particle diameter of 2 μm is weighed. Weigh the mixture to a ratio of approximately 90:10, add the molding binder, and mix uniformly.

Next, the mixed powder is filled in a mold, pressed and formed by a cold press and / or a CIP, and then sintered at a temperature of 1300 to 1500 ° C. in the air or an oxygen atmosphere. The crystal grain size of the IZO sputtering target sintered body is 3 μm or less, preferably 2 μπι or less, more preferably 1 μπι or less. If necessary, increase the density of the sintered body to 6.5 g / cm ³ or more (relative density of 92.9% or more), and further add impurities Fe, Al, Si, Ni, and T in IZ〇. Adjust i and Cu to be less than 10 ppm (wt), respectively.

The IZO sputtering target thus obtained is composed of an indium oxide crystal in which Zn is solid-dissolved or undissolved, and an In-lithium phase in which zinc is dissolved in zinc oxide crystals. It is a remarkable feature of the present invention that it has a two-phase structure of n-rich phase and that the average aggregate diameter of Zn atoms observed by EPMA is 10 m or less.

The obtained IZO sputtering target sintered body is ground with a surface grinder to obtain an IZO target material having a surface roughness of Ra 2 im or less, so that the average value of the bending strength is 68 MPa or more. Become. By setting Ra O. 5 m or less, the average value of the flexural strength becomes 78 MPa or more.

Here, the sputter surface of the IZO sputtering target may be mirror-finished so that the average surface roughness Ra is less than 0.2 μπι.

For this mirror finishing (polishing), known polishing techniques such as mechanical polishing, chemical polishing, and mechanochemical polishing (combination of mechanical polishing and chemical polishing) can be used.

For example, polishing with a fixed abrasive polisher (polishing liquid: water) or lapping with a loose abrasive wrap (abrasive material: SiC paste, etc.) and then lapping by changing the abrasive material to diamond paste Obtainable. There is no particular limitation on such a polishing method, and another polishing method may be employed as long as a good average surface roughness Ra is achieved. The obtained IZO sputtering target is bonded to a backing plate. Next, a cleaning process such as air blow or running water cleaning is performed. When removing foreign matter by air blow, it is possible to remove the foreign substance more effectively by taking in air from the opposite side of the nozzle with a dust collector. However, since there is a limit in the above-described air blow or running water cleaning, ultrasonic cleaning or the like may be further performed. It is effective to carry out this ultrasonic cleaning by performing multiple oscillations at a frequency of 25 to 300 kHz. For example, ultrasonic cleaning is preferably performed by multiplexing 12 kinds of frequencies at a frequency of 25 to 30 O KHz at intervals of 25 KHz. The bulk resistance value of the IZO sputtering target for forming a transparent conductive film formed in this manner can be set to 1ΟπιΩ · cm or less. Thus, the bulk resistance of the IZO sputtering target can be reduced without changing the conventional characteristics of the IZO.

Further, the target of the present invention is characterized in that it has a high density, has a structure in which the crystal grain size is more uniform and fine, and has a high mechanical strength. As a result, a target film S from which a transparent conductive film can be obtained stably and with good reproducibility can be obtained. Examples and comparative examples

Next, the present invention will be described with reference to examples and comparative examples.

When manufacturing an IZO sputtering target, first, weighed zinc oxide powder having the same particle size as indium oxide powder having an average particle size of 2 / zm was weighed at a ratio of about 90:10, and after uniform pulverization and mixing, Granulation was performed by adding a molding binder.

Next, this raw material mixed powder was uniformly filled in a mold and pressed by a cold press machine. The molded body thus obtained was sintered at 138 ° C. for 5 hours in a sintering furnace. The test was performed in an oxygen atmosphere during heating, in the atmosphere (atmosphere) in the other atmosphere, at a heating rate of 4 ° C / min, and a cooling rate of 10 ° C / min.

Further, the surface of the sintered body thus obtained was ground with a surface grinder, and the side was cut with a diamond cutter to obtain an Izo target material. This IZO target material was 10.7 wt% zinc oxide of zinc oxide, and had a density of 6.87 g / cm ³ (theoretical density of 7.00 g / cm ³ ). Balta resistance was 3.2 mQ cm. Further, the amounts of impurities of Fe, Al, Si, Ti, Ni, and Cu were 10 ppm or less.

Next, we observed the structure of the IZO target material and performed qualitative analysis of the target surface by EPMA. As a result, the average crystal grain size was 1.36 m. The results of the qualitative analysis by EPMA are shown in Figs. 1, 2 and 3. Figure 1 shows the results of surface analysis of indium atoms, Figure 2 shows the results of surface analysis of zinc atoms, and Figure 3 shows the results of surface analysis of oxygen atoms.

As shown in Fig. 1, Fig. 2 and Fig. 3, it can be seen that uniformly agglomerated zinc atoms are scattered in the plane. The average aggregation diameter of zinc atoms was 5 / m or less. Furthermore, the pores are smaller than the crystal grain size and are uniformly dispersed throughout.

Next, polishing was performed, and as an example of the present invention, a plate with Ra 0.4 μπι (Example 1) and a plate with surface grinding in the longitudinal direction to Ra 1.2 // m (Example 2) As a comparative example, a plate having Ra 2.2 / m by surface grinding in the longitudinal direction was prepared.

These were subjected to a three-point bending test to measure the strength. The results are shown in FIGS. Fig. 4 shows the cumulative failure probability with respect to the bending strength by the median rank method, and Fig. 5 shows the Weibull plot by the single mode.

Table 1 shows the Weibull coefficient (m value) that indicates the variation in the probability of failure from Fig. 5. The Weibull coefficient was obtained as the m value by obtaining a linear regression line. The larger the Weibull coefficient, the less variation in the maximum value of non-destructive stress is seen.From Table 1, it can be seen that the example product has less variation and is a more stable material than the conventional product. Can be confirmed.

From Fig. 4, it can be seen that when Ra is 2.0 / m or more, the bending strength decreases. Generally, the surface roughness after surface grinding corresponds to the grain size. When the particle size is not uniform, Ra becomes larger, and the bending strength is reduced accordingly. This is because the traditional organization was uneven. As is clear from the above comparison, a target having a crystal grain size of the present invention that is fine and has a small surface roughness makes it possible to obtain a target of higher quality than a conventional product.

The invention's effect

The IΖ sputtering target for forming a transparent conductive film of the present invention is substantially in bulk without substantially losing the properties of the (導電膜 Ζ Ο) transparent conductive film containing indium and zinc oxide as main components. Resistance can be effectively reduced. In addition, the bulk resistance value of the I 形成 sputtering target for forming a transparent conductive film thus formed can be controlled within the range of 1ΟπιΩ · cm or less.

Further, the target of the present invention is characterized in that it has a high density, has a structure in which the crystal grain size is more uniform and fine, and has a high transverse rupture strength. This has an excellent feature that a sputtering discharge can be stabilized and a target capable of obtaining a transparent conductive film stably and with good reproducibility can be obtained.

Claims

The scope of the claims

1. It has a two-phase structure consisting of an In-rich liquid phase in which Zn is dissolved or not dissolved in the indium oxide crystal and a Zn-rich liquid phase in which In is dissolved or not dissolved in the zinc oxide crystal. A sputtering target comprising an zinc-based zinc oxide.

2. The sputtering target comprising an indium-zinc-based oxide according to claim 1, wherein the average diameter of the aggregate of Zn atoms observed by EPMA is 10: m or less.

3. The sputtering target comprising an zinc-zinc oxide according to claim 1, wherein the average diameter of the Zn atom aggregate observed by EPMA is 5 m or less.

4. A sputtering target comprising the indium monodumbbell oxidized product according to any one of claims 1 to 3, wherein a sintered body density is 6.5 g / cm ³ or more.

5. The sputtering target comprising an zinc-zinc oxide according to any one of claims 1 to 4, wherein the sputtering target has an average crystal grain size of 3 µm or less.

6. The sputtering target comprising an indium-zinc-based oxide according to any one of claims 1 to 5, wherein the sputtering target has an average crystal grain size of 2 μm or less.

7. A sputtering target comprising the zinc-zinc oxide according to any one of claims 1 to 6, wherein the surface roughness is 2 μπι or less in Ra and the average bending strength is 68 MPa or more. .

8. It is composed of the aluminum oxide of the dumbbell type according to any one of claims 1 to 6, wherein the surface roughness is 0.5 im or less in Ra and the average bending strength is 78 MPa or more. Sputtering target.

9. The amount of impurities in the indium-zinc-based oxide sintered body, Fe, A, Si, Ni, Ti, and 11 each being 10 111 (wt) or less. A notching target composed of the zinc-based zinc oxide described in 1 to 8 above.

10. Indium oxide and zinc oxide are finely pulverized, mixed and granulated, molded by cold pressing and / or cold isostatic pressing, and then heated and sintered at 1300 to 1500 ° C in an oxygen atmosphere or air. It is characterized by the following two phases: a Zn-rich phase in which Zn is solid-dissolved or insoluble in ZnO crystal and a Zn-rich phase in which Zn is solid-dissolved or insoluble in ZnO crystal. A method for producing a sputtering target comprising an indium-zinc oxide having a texture.

11. The method for producing a sputtering target comprising an indium-zinc-based oxide according to claim 10, wherein the diameter of the aggregate of Zn atoms observed by EPMA is 1 O / zm or less.

12. The method for producing a sputtering target comprising an indium-zinc-based acid according to claim 10 or 11, wherein the density of the sintered body is 6.5 gZ cm ³ or more.

13. The method for producing a sputtering target comprising an indium-zinc oxide according to any one of claims 10 to 12, wherein the average crystal grain size is 3 µm or less.

1. The method for producing a sputtering target comprising an indium-zinc-based oxide according to any one of claims 10 to 12, wherein the average crystal grain size is 2 µm or less.

15. The sputtering tool comprising an indium-zinc-based oxide according to any one of claims 10 to 14, wherein the surface roughness is Ra; 2; zm or less, and the average bending strength is 68 MPa or more. One get manufacturing method.

16. The indium-zinc oxide according to any one of claims 10 to 15, wherein the surface roughness is 0.5 m or less in Ra and the average bending strength is 78 MPa or more. Method for producing a sputtering target.

17. The claim wherein the impurities in the indium-zinc-based oxide sintered body, Fe, Al, Si, Ni, Ti, and Cu, are each less than lOppm (wt). Item 17. A method for producing a sputtering target comprising the indium-zinc oxide according to any one of Items 10 to 16.