Indium oxide transparent conductive film

Abstract

An indium oxide sintered compact containing zirconium as an additive, wherein the ratio of atomic concentration of zirconium to the sum of the atomic concentration of indium and the atomic concentration of zirconium is in the range of 0.5 to 4%, the relative density is 99.3% or higher, and the bulk resistance is 0.5 m.Math.cm or less. An indium oxide transparent conductive film of high transmittance in the visible light region and the infrared region, with low film resistivity, and in which the crystallization temperature can be controlled, as well as the manufacturing method thereof, and an oxide sintered compact for use in producing such transparent conductive film are provided.

Claims

1. An indium oxide transparent conductive film containing zirconium as an additive, wherein a ratio of atomic concentration of zirconium to a sum of that of indium and zirconium is in a range of 0.5 to 4%, resistivity is 410.sup.4.Math.cm or less, electron mobility is 50 cm.sup.2/V.Math.s or more, transmittance in a wavelength of 1200 nm is 90% or higher, and the indium oxide transparent conductive film is crystalline.

2. An indium oxide transparent conductive film containing zirconium as an additive and tin in addition to the additive, wherein a ratio of atomic concentration of zirconium to a sum of that of indium and zirconium is in a range of 0.5 to 4%, a ratio of atomic concentration of tin to a sum of that of indium, zirconium and tin is in a range of 0.015 to 0.5%, resistivity is 410.sup.4.Math.cm or less, electron mobility is 50 cm.sup.2/V.Math.s or more, transmittance in a wavelength of 1200 nm is 90% or higher, and the indium oxide transparent conductive film is crystalline.

3. The indium oxide transparent conductive film according to claim 2 containing at least one of magnesium and calcium in addition to the additive, wherein a ratio of atomic concentration of magnesium or calcium or a sum of the atomic concentrations thereof to a sum of that of all metal elements of the film is in the range of 0.5 to 2.0%, the resistivity is 410.sup.4.Math.cm or less, the electron mobility is 50 cm.sup.2/V.Math.s or more, the transmittance in a wavelength of 1200 nm is 90% or higher, and the indium oxide transparent conductive film is crystalline.

Description

EXAMPLES

Example 1

(1) Indium oxide (In.sub.2O.sub.3) raw material powder and zirconium oxide (ZrO.sub.2) raw material powder with an average grain size of approximately 2.0 m were weighed so that the ratio of atomic concentration of zirconium to the sum of the atomic concentration of indium and the atomic concentration of zirconium becomes 1%, and these raw material powders were mixed with a super mixer in the atmosphere at a rotation speed of 3000 rpm and rotation time of 3 minutes. The mixed powder was placed in an attritor together with zirconia beads and pulverized at a rotation speed of 300 rpm and rotation time of 3 hours to achieve an average grain size (D50) of 0.8 m. The water volume was adjusted so that the pulverized raw material became a slurry with a solid content of 50%, and granulation was performed by setting the inlet temperature to 200 C. and the outlet temperature to 120 C. In addition, the granulated powder was press molded in the following conditions; namely, surface pressure of 600 kgf/cm.sup.2 and retention time of 1 minute, and thereafter molded based on cold isostatic press (CIP) in the following conditions; namely, surface pressure of 1800 kgf/cm.sup.2 and retention time of 1 minute. Thereafter, the molded article was sintered using an electric furnace in an oxygen atmosphere at 1550 C. for 20 hours. The relative density of the obtained sintered compact was 99.3%, and the bulk resistance was 0.47 m.Math.cm.

(2) This sintered compact was ground to a disk shape with a diameter of 6 inches and a thickness of 6 mm, and thereby processed into a sputtering target. This target was placed in a sputtering device and deposited, via sputtering, on a non-heated glass substrate in an argon atmosphere at a pressure of 0.5 Pa in order to obtain an amorphous transparent conductive film. As a result of subjecting this film to Hall measurement, the resistivity was 0.765 m.Math.cm, the mobility was 15.2 cm.sup.2/V.Math.s, and it was confirmed that the film was amorphous since an XRD diffraction peak could not be acknowledged. Here, the transmittance of the film was 86.7% in a wavelength of 1200 nm.

(3) The obtained amorphous transparent conductive film was annealed in a nitrogen atmosphere for 1 hour, and, upon subjecting the film to Hall measurement and XRD diffraction measurement, since the sharp decline in the resistivity of the film and appearance of the XRD diffraction peak were acknowledged when the heating temperature was 155 C., the crystallization temperature of this film was recognized as being 155 C.

(4) Upon subsequently annealing this film at 185 C., which is a temperature that is 30 C. higher than the crystallization temperature and subjecting the film to Hall measurement, the resistivity was 0.395 m.Math.cm, the mobility was 68.5 cm.sup.2/V.Math.s, and the transmittance in a wavelength of 1200 nm was 92.1%.

(5) TABLE-US-00001 Ratio Ratio Ratio Ratio Perme- Perme- of Zr of Sn of Mg of Ca Oxy- Resis- Film ability Resis- Film ability Atomic Atomic Atomic Atomic Rela- gen tivity Mobility Crystal- after tivity Mobility after Con- Con- Con- Con- tive Bulk Con- after after ization Depo- after after Anneal- cen- cen- cen- cen- Den- Resis- cen- Depo- Depo- Tem- sition Anneal- Anneal- ing tration tration tration tration sity tance tration sition sition perature (at 1200 ing ing (at 1200 Examples (%) (%) (%) (%) (%) (mcm) (%) (mcm) (cm2/Vs) ( C.) nm) (%) (mcm) (cm2/Vs) nm) (%) Example 1 1 0 0 0 99.3 0.47 0 0.765 15.2 155 86.7 0.395 68.5 92.1 Example 2 2 0 0 0 99.4 0.45 0 0.748 16.0 160 87.7 0.385 64.6 93.1 Example 3 3 0 0 0 99.5 0.46 0 0.590 23.6 170 87.1 0.321 70.1 93.0 Example 4 4 0 0 0 99.4 0.48 0 0.675 20.0 170 87.3 0.365 55.2 92.8 Com- 0.3 0 0 0 98.3 0.48 0 0.855 13.7 150 86.5 0.523 48.2 91.3 parative Example 1 Com- 5 0 0 0 98.6 0.49 0 0.896 12.1 180 86.9 0.612 44.6 91.5 parative Example 2 Example 5 2 0.02 0 0 99.7 0.43 0 0.747 15.8 160 87.7 0.388 64.2 93.2 Example 6 2 0.12 0 0 99.8 0.44 0 0.741 16.2 160 87.6 0.381 64.7 93.1 Example 7 2 0.23 0 0 99.8 0.43 0 0.745 15.7 160 87.8 0.378 64.1 93.1 Example 8 2 0.47 0 0 99.9 0.43 0 0.732 16.0 160 87.7 0.387 64.9 93.2 Com- 2 0.7 0 0 99.9 0.44 0 0.722 15.5 160 87.7 0.371 64.7 93.1 parative Example 3 Example 9 2 0.12 0.5 0 99.7 0.44 0 0.739 16.5 180 87.6 0.381 67.2 93.1 Example 10 2 0.12 1.0 0 99.8 0.44 0 0.740 16.7 205 87.3 0.383 65.3 93.3 Example 11 2 0.12 1.5 0 99.7 0.45 0 0.759 16.3 220 87.5 0.385 64.1 93.2 Example 12 2 0.12 2.0 0 99.8 0.46 0 0.765 15.5 245 87.7 0.391 62.2 93.3 Example 13 2 0.12 0 0.5 99.7 0.44 0 0.739 16.2 185 87.8 0.379 67.1 93.4 Example 14 2 0.12 0 1.0 99.6 0.44 0 0.742 16.1 210 87.4 0.381 65.3 93.0 Example 15 2 0.12 0 1.5 99.7 0.45 0 0.755 16.3 230 87.5 0.385 63.5 93.2 Example 16 2 0.12 0 2.0 98.8 0.46 0 0.765 15.5 255 87.6 0.398 61.3 93.2 Example 17 2 0.12 0.25 0.25 99.8 0.44 0 0.740 16.4 185 87.4 0.385 66.8 93.3 Example 18 2 0.12 0.5 0.5 99.7 0.44 0 0.746 16.2 210 87.5 0.388 64.8 93.4 Example 19 2 0.12 0.75 0.75 99.8 0.45 0 0.761 15.9 230 87.6 0.392 64.1 93.3 Example 20 2 0.12 1 1 99.9 0.46 0 0.778 15.7 255 87.6 0.396 61.5 93.2 Com- 2 0.12 3 0 99.6 0.47 0 0.789 15.2 285 87.8 0.388 60.3 93.1 parative Example 4 Com- 2 0.12 0 3 99.6 0.47 0 0.791 15.3 300 87.5 0.392 59.6 93.0 parative Example 5 Com- 2 0.12 1.5 1.5 99.6 0.47 0 0.782 15.2 290 87.6 0.393 60.2 93.0 parative Example 6 Com- 2 0.12 0 0 99.8 0.44 1 0.838 11.1 160 87.3 0.773 40.3 90.3 parative Example 7 Com- 0 10 0 0 99.9 0.22 0 0.745 8.6 160 71.3 0.320 15.3 69.0 parative Example 8 Com- 0 10 0 0 99.9 0.22 1 0.820 9.1 160 79.0 0.290 17.1 73.0 parative Example 9 Com- 2 0 0 0 93.2 0.87 0 1.375 4.6 165 83.2 0.786 9.2 84.3 parative Example 10 Com- 2 0.12 0 0 91.2 0.91 0 1.567 3.7 165 79.8 0.832 8.7 82.1 parative Example 11

Examples 2 to 4, Comparative Examples 1 and 2

(6) The manufacturing method of the sintered compact and the transparent conductive film were the same as Example 1, and only the ratio of atomic concentration of zirconium was changed. The results are shown in Table 1. From these results, it is evident that, when the ratio of atomic concentration of zirconium falls outside of the range of 0.5 to 4%, the resistivity of the film becomes high after sputtering deposition and after annealing and the mobility becomes low, which shows undesirable characteristics as a transparent conductive film. Moreover, even in cases where tin is not added, the relative density is 99.3% or higher, and even 99.5% or higher, and it is evident that high density has been obtained.

Examples 5 to 8, Comparative Example 3

(7) The manufacturing method of the sintered compact and the manufacturing method of the transparent conductive film were the same as Example 1, the ratio of atomic concentration of zirconium was set to 2%, and only the ratio of atomic concentration of tin was changed. The results are shown in Table 1. From these results, it is evident that the relative density is comparatively high at 99.3% even in cases where the tin concentration was zero as in Example 1, but as a result of adding tin, the relative density became 99.5% or higher, and even 99.7% or higher, and it was possible to achieve even higher density. Meanwhile, it can be seen that the improvement in the density becomes saturated when the ratio of atomic concentration of tin is 0.5% or higher.

Examples 9 to 20, Reference Examples 4 to 6

(8) The manufacturing method of the sintered compact and the manufacturing method of the transparent conductive film were the same as Example 1, the ratio of atomic concentration of zirconium was set to 2%, the ratio of atomic concentration of tin was set to 0.12%, and the ratio of atomic concentration of magnesium or the ratio of atomic concentration of calcium was changed. The results are shown in Table 1. From these results, it is evident that, by adding these elements, the crystallization temperature can be increased. Meanwhile, when the concentration of these elements exceeds 2.0%, it can be seen that the crystallization temperature becomes too high and this is undesirable.

Reference Example 7

(9) The manufacturing method of the sintered compact and the manufacturing method of the transparent conductive film were the same as Example 1, the ratio of atomic concentration of zirconium was set to 2%, the ratio of atomic concentration of tin was set to 0.12%, magnesium and the like were not added, and the atmosphere gas during sputtering was 1% oxygen. The results are shown in Table 1. From these results, it is evident that, if the oxygen concentration is high, the resistivity of the film after deposition and after crystallization becomes high and the mobility becomes low.

Comparative Examples 8 and 9

(10) The manufacturing method of the sintered compact and the manufacturing method of the transparent conductive film were the same as Example 1, and the indium oxide raw material powder and the tin oxide raw material powder were used, and the additive amount of the tin oxide raw material powder was set to be comparable to a standard ITO. In Comparative Example 8, the oxygen concentration during the sputtering deposition was set to 0%, and, in Comparative Example 9, the oxygen concentration during the sputtering deposition was set to 1%. The results of the sintered compact and film characteristics are as described in Table 1. From these results, it can be seen that ITO has high carrier concentration and low transmittance in a long wavelength (1200 nm) since the mobility is low in cases of equivalent resistivity when compared with the present invention.

Comparative Examples 10 and 11

(11) The manufacturing method of the sintered compact and the transparent conductive film were the same as Example 1, and the sintering temperature was set to 1350 C. In Comparative Example 10, the ratio of atomic concentration of zirconium was set to 2%, and, in Comparative Example 11, the ratio of atomic concentration of zirconium was set to 2% and the ratio of atomic concentration of tin was set to 0.12%. The results of the sintered compact and film characteristics are as described in Table 1. From these results, it can be seen that a film obtained based on sputtering deposition from a sintered compact with a low relative density and high bulk resistance by lowering the sintering temperature has high resistivity and low transmittance in a long wavelength (1200 nm), and is undesirable.

(12) Since the indium oxide sintered compact of the present invention has high density, it is possible to inhibit the generation of nodules on its surface and prevent abnormal discharge in the sputtering process when this sintered compact is used as the sputtering target. Moreover, since the indium oxide sintered compact of the present invention has low bulk resistivity, it is possible to reduce the resistivity of the film formed by sputtering, and this is effective in faulting a transparent conductive film. In addition, since the indium oxide transparent conductive film of the present invention has high transmittance in the visible light region and the infrared region, as well as high electron mobility and low film resistivity, it is extremely effective as a transparent conductive film for use in solar batteries.