Sintered oxide, method for its production, and sputtering target

Abstract

The purpose of the present invention is to provide a sintered oxide to be used for a sputtering target, whereby little abnormal discharge occurs even during high-power film-deposition and no cracking occurs in the target. A sintered oxide having zinc, aluminum, titanium and oxygen, as constituent elements, characterized in that when the contents of zinc, aluminum and titanium are represented by Zn, Al, and Ti, respectively, the atomic ratios of the elements constituting the sintered oxide are
Al/(Zn+Al+Ti)=0.035 to 0.050 and
Ti/(Zn+Al+Ti)=0.05 to 0.20,
and the average grain size of crystal grains having a Zn.sub.2TiO.sub.4 crystal phase as the matrix phase in the sintered oxide, is at most 5 m.

Claims

1. A sintered oxide having zinc, aluminum, titanium and oxygen as constituent elements, characterized in that when the contents of zinc, aluminum and titanium are represented by Zn, Al, and Ti, respectively, the atomic ratios of the elements constituting the sintered oxide are
Al/(Zn+Al+Ti)=0.035 to 0.050 and
Ti/(Zn+Al+Ti)=0.05 to 0.20, and the average grain size of crystal grains having a Zn.sub.2TiO.sub.4 crystal phase as the matrix phase in the sintered oxide, is at most 5 m.

2. The sintered oxide according to claim 1, characterized in that crystal grains having a Zn.sub.2TiO.sub.4 crystal phase as the matrix phase and having a grain size exceeding 20 m, are not present in the sintered oxide.

3. The sintered oxide according to claim 1, characterized in that in the X-ray diffraction of the sintered oxide, no diffraction peak of aluminum oxide phase is present.

4. The sintered oxide according to claim 1, characterized in that the relative density is at least 98%.

5. The sintered oxide according to claim 1, characterized in that the bending strength is at least 150 MPa.

6. A sputtering target characterized by using the sintered oxide as defined in claim 1, as target material.

Description

EXAMPLES

(1) Now, the present invention will be described in further detail with reference to Examples, but the present invention is not limited thereto. Here, various measurements in Examples were carried out as follows.

(2) (1) BET Specific Surface Area of Powder

(3) The BET specific surface area of a powder was measured by a gas adsorption method by means of a specific surface area measuring apparatus (TriStar 3000, manufactured by Shimadzu Corporation).

(4) (2) Particle Size Measurement of Powder

(5) The particle size of a powder was measured by a laser diffraction scattering method by means of a particle size distribution measuring apparatus (SALD-7100, manufactured by Shimadzu Corporation), to obtain D50 (50% diameter) and 090 (90% diameter) in a volume frequency distribution.

(6) (3) Density of Sintered Oxide

(7) For the relative density of a sintered oxide, the bulk density was measured by the Archimedes method in conformity with JIS R 1634, and the relative density was obtained by dividing the bulk density by the true density. The true density of the sintered oxide was calculated from the arithmetic average represented by the following formula, wherein when Zn, Ti and Al in the sintered oxide are converted to oxides and represented by zinc oxide, titanium oxide and aluminum oxide, respectively, the respective amounts are a (g), b (g), and c (g), and the respective true densities are 5.606 (g/cm.sup.3), 3.95 (g/cm.sup.3) and 4.23 (g/cm.sup.3):
d=(a+b+c)/((a/5.606)+(b/3.95)+(c/4.23))
(4) X-Ray Diffraction Test

(8) The X-ray diffraction pattern in a range of 2=20 to 70 of a mirror-polished sintered oxide sample was measured.

(9) Scanning method: step-scan method (FT method)

(10) X-ray source: CuK

(11) Power: 40 kV, 40 mA

(12) Step width: 0.01

(13) (5) Crystal Grain Size

(14) A sample was mirror-polished, and the ZnO phase and the Zn.sub.2TiO.sub.4 phase were identified by a composition analysis by EPMA, whereupon the crystal grain size was measured by a diameter method from the SEM image. The sample was observed at optional three or more points, and for each, at least 300 grains were measured.

(15) (EPMA Analysis Conditions)

(16) Apparatus: wavelength dispersive electron beam micro-analyzer

(17) Accelerating voltage: 15 kV

(18) Irradiation current: 30 nA

(19) (6) Bending Strength

(20) Measured in accordance with JIS R 1601.

(21) (Conditions for Measurement of Bending Strength)

(22) Test method: 3-point bending test

(23) Distance between fulcrums: 30 mm

(24) Sample size: 3 mm4 mm40 mm

(25) Head speed: 0.5 mm/min

(26) (7) Bulk Resistance

(27) An obtained sintered oxide was processed into a size of about 10 mm20 mm1 mmt, and a silver paste was applied to contact points (4 points) of the measuring probe, followed by measurement by a 4-terminal method by means of a particle size distribution measuring apparatus (Loresta HP MCP-T410, manufactured by Mitsubishi Petrochemical Co., Ltd.).

(28) (8) Sputtering Evaluation

(29) An obtained sintered oxide was processed into a size of 101.6 mm6 mmt and then bonded to a backing plate of oxygen-free copper by indium solder to obtain a sputtering target. By using this target, sputtering was carried out by varying the input power under the following conditions, whereby arcing measurement and observation of target cracking were conducted.

(30) (Sputtering Conditions)

(31) Gas: argon+oxygen (3%)

(32) Pressure: 0.6 Pa

(33) Power source: DC

(34) Input power: 400 W (4.9 W/cm.sup.2) 600 W (7.4 W/cm.sup.2) 800 W (9.9 W/cm.sup.2)

(35) Discharge time: 120 min each

(36) Arcing measurement condition (threshold voltage): sputtering voltage 50 [V].

Example 1

(37) Zinc oxide powder, titanium oxide powder and a powder of aluminum oxide (a) having the powder properties as shown in Table 1, were weighed to attain the ratios of Al/(Zn+Al+Ti)=0.045 and Ti/(Zn+Al+Ti)=0.05. The weighed powders and iron core-containing resin balls having a diameter of 15 mm were put in a polyethylene pot and mixed for 20 hours by a dry ball mill. The powder after mixing was passed through a 300 m sieve and molded by a mold press under a pressure of 300 kg/cm.sup.2 to prepare a molded product of 120 mm120 mm8 mmt, followed by CIP treatment under a pressure of 2 ton/cm.sup.2.

(38) Then, the molded product was placed on an alumina setter and fired in a resistance heating type electric furnace under the following conditions (furnace capacity: 250 mm250 mm250 mm). The evaluation results of the obtained sintered oxide are shown in Table 2, and the sputtering evaluation results of the obtained sputtering target are shown in Table 3.

(39) (Firing Conditions)

(40) Firing temperature: 1100 C.

(41) Holding time: 1 hour

(42) Temperature raising rate: 100 C./hr

(43) Atmosphere: oxygen flow atmosphere (200 mL/min)

(44) Temperature lowering rate: 300 C./hr.

Example 2

(45) Using zinc oxide powder, titanium oxide powder and a powder of aluminum oxide (a) having the powder properties as shown in Table 1, in the ratios of Al/(Zn+Al+Ti)=0.040 and Ti/(Zn+Al+Ti)=0.1, a CIP treatment molded product was obtained under the same conditions as in Example 1. This molded product was placed on an alumina setter and fired in a resistance heating type electric furnace under the same conditions as in Example 1 except that the firing temperature was changed to 1200 C. and the holding time was changed to 3 hours. The evaluation results of the obtained sintered oxide are shown in Table 2, and the sputtering evaluation results of the obtained sputtering target are shown in Table 3.

Example 3

(46) Using zinc oxide powder, titanium oxide powder and a powder of aluminum oxide (b) having the powder properties as shown in Table 1, in the ratios of Al/(Zn+Al+Ti)=0.038 and Ti/(Zn+Al+Ti)=0.19, a CIF treatment molded product was obtained under the same conditions as in Example 1, This molded product was placed on an alumina setter and fired in a resistance heating type electric furnace under the same conditions as in Example 1 except that the firing temperature was changed to 1300 C., and the holding time was changed to 5 hours. The evaluation results of the obtained sintered oxide are shown in Table 2, and the sputtering evaluation results of the obtained sputtering target are shown in Table 3.

Example 4

(47) A sintered oxide was prepared under the same conditions as in Example 3 except that the mixing time in the dry ball mill was changed to 10 hours. The evaluation results of the obtained sintered oxide are shown in Table 2, and the sputtering evaluation results of the obtained sputtering target are shown in Table 3.

Example 5

(48) A CIP treatment molded product was obtained under the same conditions as in Example 2 except that in the process for the preparation of the mixed powder, a wet bead mill and a spray dryer were used under the following conditions, and the obtained powder was passed through a sieve of 150 m. This molded product was placed on an alumina setter and fired in a resistance heating type electric furnace under the same conditions as in Example 2 except that the holding time was changed to 1 hour.

(49) (Bead Mill Conditions)

(50) Bead diameter: 0.3 mm

(51) Beads filling rate: 85%

(52) Peripheral speed: 7 m/sec

(53) Number of passes: 10 times

(54) Slurry concentration: powder 60 wt %

(55) (Spray Dryer Conditions)

(56) Hot air temperature: inlet 180 C., exit 120 C.

(57) Disk rotation number: 10000 rpm

(58) The evaluation results of the obtained sintered oxide are shown in Table 2, and the sputtering evaluation results of the obtained sputtering target are shown in Table 3.

(59) (Film Deposition Evaluation)

(60) The film deposition was conducted under the following conditions using a sputtering target obtained in each of Examples 1 to 5, and thin film resistances were measured. Thin film resistances were all at least 10.sup.5, i.e. high-resistance films.

(61) (Sputtering Conditions)

(62) Gas: argon+oxygen (3%)

(63) Pressure: 0.6 Pa

(64) Power source: DC

(65) Input power: 400 W (4.9 W/cm.sup.2)

(66) Film thickness: 80 nm

(67) Substrate: alkali-free glass (EAGLE XG manufactured by Corning, thickness: 0.7 Mm)

(68) (Conditions for Measurement of Resistance)

(69) Apparatus: Loresta HP (MCP-T410, manufactured by Mitsubishi Petrochemical Co., Ltd.)

(70) Measurement method: four-terminal method.

Comparative Example 1

(71) Using zinc oxide powder, titanium oxide powder and a powder of aluminum oxide (a) having the powder properties as shown in Table 1, in the ratios of Al/(Zn+Al+Ti)=0.025 and Ti/(Zn+Al+Ti)=0.10, a CIP treatment molded product was obtained under the same conditions as in Example 1. This molded product was placed on an alumina setter and fired in a resistance heating type electric furnace under the same conditions as in Example 1 except that the firing temperature was changed to 1250 C. and the holding time was changed to 5 hours. The evaluation results of the obtained sintered oxide are shown in Table 2, and the sputtering evaluation results of the sputtering target are shown in Table 3.

Comparative Example 2

(72) Using zinc oxide powder, titanium oxide powder and a powder of aluminum oxide (a) having the powder properties as shown in Table 1, in the ratios of Al/(Zn+Al+Ti)=0.025 and Ti/(Zn+Al+Ti)=0.10, a CIP treatment molded product was obtained under the same conditions as in Example 1. This molded product was placed on an alumina setter and fired in a resistance heating type electric furnace under the same conditions as in Example 1 except that the firing temperature was changed to 1350 C. and the holding time was changed to 10 hours. The evaluation results of the obtained sintered oxide are shown in Table 2, and the sputtering evaluation results of the sputtering target are shown in Table 3.

Comparative Example 3

(73) Using zinc oxide powder, titanium oxide powder and a powder of aluminum oxide (c) having the powder properties as shown in Table 1, in the ratios of Al/(Zn+Al+Ti)=0.040 and Ti/(Zn+Al+Ti)=0.10, a CIP treatment molded product was obtained under the same conditions as in Example 1. This molded product was placed on an alumina setter and fired in a resistance heating type electric furnace under the same conditions as in Example 1 except that the firing temperature was changed to 1250 C. and the holding time was changed to 5 hours. The evaluation results of the obtained sintered oxide are shown in Table 2, and the sputtering evaluation results of the sputtering target are shown in Table 3.

Comparative Example 4

(74) Using zinc oxide powder, titanium oxide powder and a powder of aluminum oxide (c) having the powder properties as shown in Table 1, in the ratios of Al/(Zn+Al+Ti)=0.040 and Ti/(Zn+Al+Ti)=0.10, a CIF treatment molded product was obtained under the same conditions as in Example 1. This molded product was placed on an alumina setter and fired in a resistance heating type electric furnace under the same conditions as in Example 1 except that the firing temperature was changed to 1350 C. and the holding time was changed to 10 hours. The evaluation results of the obtained sintered oxide are shown in Table 2, and the sputtering evaluation results of the sputtering target are shown in Table 3.

Comparative Example 5

(75) Using zinc oxide powder, titanium oxide powder and a powder of aluminum oxide (a) having the powder properties as shown in Table 1, in the ratios of Al/(Zn+Al+Ti)=0.040 and Ti/(Zn+Al+Ti)=0.25, a CIP treatment molded product was obtained under the same conditions as in Example 1, This molded product was placed on an alumina setter and fired in a resistance heating type electric furnace under the same conditions as in Example 1 except that the firing temperature was changed to 1350 C. and the holding time was changed to 5 hours. The evaluation results of the obtained sintered oxide are shown in Table 2. Since the obtained sintered oxide had a high bulk resistance, the sputtering evaluation was not conducted.

Example 6

(76) Nine sheets of CIP treated molded product were obtained under the same conditions as in Example 2 except that molded products of 351 mm477 mm8 mmt were prepared under a pressure of 1 ton/cm.sup.2 using a CIP molding type mold instead of the mold press, followed by CIP treatment under a pressure of 2 ton/cm.sup.2. Then, these molded products were set on alumina setters and fired in a resistance heating type electric furnace (furnace capacity: 1500 mm1200 mm600 mm) under the same conditions as in Example 2 except that the oxygen flow rate was changed to 120 L/min. The obtained sintered oxides were processed into a size of 310 mm420 mm6 mmt, to obtain nine sheets of sintered oxide having no cracks. Then, three sheets of sintered oxide were bonded, as one set, to a backing plate of oxygen-free copper by indium solder to obtain a sputtering target. In this manner, three sputtering targets were obtained. The evaluation results of the obtained sintered oxides are shown in Table 2.

Example 7

(77) Nine molded products were obtained under the same conditions as in Example 2 except that molded products having an inner diameter of 86 mman outer diameter of 116 mma length of 200 mm were prepared under a pressure of 2 ton/cm.sup.2 using a CIP molding type mold instead of the mold press. Then, these molded products were set on alumina setters and fired in a resistance heating type electric furnace under the same conditions as in Example 2. The obtained sintered oxides were processed into an inner diameter of 77 mman outer diameter of 91 mma length of 170 mm, to obtain nine sintered oxides having no cracks. Then, three sintered oxides were bonded, as one set, to a titanium backing plate by indium solder to obtain a sputtering target. In this manner, three sputtering targets were obtained. The evaluation results of the obtained sintered oxides are shown in Table 2.

(78) TABLE-US-00001 TABLE 1 Average grain size D50 D90 BET Raw material m m m.sup.2/g ZnO 0.95 1.86 3.75 TiO.sub.2 1.05 2.02 6.8 Al.sub.2O.sub.3 (a) 0.16 0.31 16.5 Al.sub.2O.sub.3 (b) 0.36 0.64 10.3 Al.sub.2O.sub.3 (c) 0.95 1.26 8.3

(79) TABLE-US-00002 TABLE 2 BET increase value of mixed Firing Al.sub.2O.sub.3 Composition powder relative temper- Holding raw Al/Zn + Ti/Zn + to ZnO powder ature time Density material Al + Ti Al + Ti (m.sup.2/g) ( C.) (hr) (%) Ex. 1 Al.sub.2O.sub.3 (a) 0.045 0.05 1.19 1100 1 >98 Ex. 2 Al.sub.2O.sub.3 (a) 0.040 0.10 1.33 1200 3 >98 Ex. 3 Al.sub.2O.sub.3 (b) 0.038 0.19 1.45 1300 5 >98 Ex. 4 Al.sub.2O.sub.3 (b) 0.038 0.19 0.93 1300 5 >98 Ex. 5 Al.sub.2O.sub.3 (a) 0.040 0.10 2.98 1200 1 >98 Comp. Ex. 1 Al.sub.2O.sub.3 (a) 0.025 0.10 1.18 1250 5 97 Comp. Ex. 2 Al.sub.2O.sub.3 (a) 0.025 0.10 1.18 1350 10 >98 Comp. Ex. 3 Al.sub.2O.sub.3 (c) 0.040 0.10 0.97 1250 5 >98 Comp. Ex. 4 Al.sub.2O.sub.3 (c) 0.040 0.10 0.97 1350 10 >98 Comp. Ex. 5 Al.sub.2O.sub.3 (a) 0.040 0.25 1.62 1350 5 >98 Ex. 6 Al.sub.2O.sub.3 (a) 0.040 0.10 1.33 1200 3 >98 Ex. 7 Al.sub.2O.sub.3 (a) 0.040 0.10 1.33 1200 3 >98 X-ray Average grain size Maximum grain size Bending Bulk diffraction Zn.sub.2TiO.sub.4 (abnormal grains) strength resistance peak of ZnO phase phase Zn.sub.2TiO.sub.4 phase (MPa) (cm) Al.sub.2O.sub.3 (m) (m) (m) Ex. 1 205 2.0 10.sup.3 No 1.29 0.9 3.2 Ex. 2 202 4.1 10.sup.3 No 1.35 1.59 6.8 Ex. 3 212 4.6 10.sup.2 No 1.39 3.46 9.8 Ex. 4 163 5.4 10.sup.2 No 1.42 4.2 13.2 Ex. 5 235 3.2 10.sup.3 No 1.21 1.01 2.8 Comp. Ex. 1 122 2.3 10.sup.1 Yes 1.41 6.1 22.6 Comp. Ex. 2 92 1.0 10.sup.1 Yes 1.61 8.5 30.9 Comp. Ex. 3 133 6.7 10.sup.3 Yes 1.65 5.59 20.3 Comp. Ex. 4 103 5.8 10.sup.3 Yes 1.65 11.3 38.5 Comp. Ex. 5 108 3.2 10.sup.4 Yes 1.58 7.1 28.3 Ex. 6 200 5.1 10.sup.3 No 1.33 1.61 6.5 Ex. 7 208 4.6 10.sup.3 No 1.31 1.56 6.0

(80) TABLE-US-00003 TABLE 3 Arcing 400 W 600 W 800 W Number Number Number of of of arcings Cracking arcings Cracking arcings Cracking Ex. 1 3 No 10 No 25 No Ex. 2 5 No 13 No 36 No Ex. 3 6 No 19 No 38 No Ex. 4 9 No 27 No 63 No Ex. 5 4 No 11 No 21 No Comp. 22 No 121 Yes 354 Yes Ex. 1 Comp. 36 No 155 Yes 466 Yes Ex. 2 Comp. 18 No 91 Yes 264 Yes Ex. 3 Comp. 24 No 139 Yes 503 Yes Ex. 4

(81) The present invention has been described in detail and with reference to specific Examples, but it is apparent to those skilled in the art that various changes and modifications can be made without departing from the spirit and scope of the present invention.

(82) The entire disclosure of Japanese Patent Application No, 2014-156608 filed on Jul. 31, 2014 including specification, claims, drawings and summary is incorporated herein by reference in its entirety.