KR20170069933A - Sputtering target material - Google Patents

Abstract

Provided is a sputtering target material capable of suppressing occurrence of cracking in handling of a sputtering target material during machining or in a reversing operation in a bonding process.
Wherein the oxide sintered body contains 20 atom% to 50 atom% of Sn and 50 atom% to 80 atom% of Zn with respect to the whole metal component, and one pore having a circle equivalent diameter exceeding 2.0 탆 per 1050 탆 ² , . The average value of the relative density is preferably 98.5% or more, and the deviation from the average value is more preferably 0.3% or less.

Description

[0001] SPUTTERING TARGET MATERIAL [0002]

The present invention relates to a sputtering target material comprising an oxide sintered body used for forming an oxide semiconductor layer of a thin film transistor for driving a large liquid crystal display or an organic EL display, for example.

2. Description of the Related Art In a display device such as a liquid crystal display or an organic EL display driven by a thin film transistor (hereinafter referred to as " TFT "), an amorphous silicon film or a crystalline silicon film is used as a channel layer of a TFT. Along with the demand for high definition display, oxide semiconductors have attracted attention as a material used for a channel layer of a TFT. For example, an oxide semiconductor film containing In (indium), Ga (gallium), Zn (zinc) and O (oxygen) (hereinafter referred to as "IGZO thin film") has excellent TFT characteristics, . In and Ga contained in the thin film of I-G-Z-O are rare and expensive metals designated in Japan as rare metals to be stored.

Therefore, a Zn-Sn-O-based oxide semiconductor film (hereinafter referred to as a "ZTO thin film") has been attracting attention as an oxide semiconductor film containing no In or Ga contained in the I-G-Z-O thin film. The ZTO thin film is formed by a sputtering method using a sputtering target. This sputtering method is a method in which ions, atoms or clusters collide against a sputtering target surface, and the surface of the material is shaved (or scattered), thereby depositing the components constituting the material on the surface of a substrate or the like .

Here, since the ZTO thin film is a thin film containing oxygen, the so-called reactive sputtering method in which the film is formed in an atmosphere containing oxygen is used in the sputtering method. This reactive sputtering method is a method of sputtering in an atmosphere of a mixed gas composed of an argon gas and an oxygen gas and sputtering while reacting ions, atoms or clusters with oxygen to form an oxide thin film.

The sputtering target used in this reactive sputtering method is used in a state where a sputtering target material composed of a ZTO-based oxide sintered body having a composition approximate to that of the ZTO thin film is bonded to a backing plate with a brazing material.

For example, in Patent Document 1, a predetermined amount of a ZnO powder and a SnO ₂ powder are mixed as a sputtering target material comprising a ZTO-based oxide sintered body, mixed and assembled in a ball mill, and calcined powder preliminarily fired is prepared , A method is proposed in which the calcined powder is reassembled and molded to produce a molded body, followed by firing.

Japanese Patent Application Laid-Open No. 2010-37161

According to the study by the present inventors, the sputtering target material made of the ZTO-based oxide sintered body manufactured by the method disclosed in the above-mentioned Patent Document 1 is cracked during machining or cracked during handling such as reversing work in the bonding step And the like.

It is an object of the present invention to solve the above problems and to provide a sputtering target material which is less prone to cracking during handling such as machining or reversing work in a bonding process.

As a result of studying the above problems, the inventor of the present invention has found that cracks generated in the ZTO-based oxide sintered body sputtering target are caused by vacancies existing in the sputtering target material. The present invention has been accomplished on the basis of this finding that the problem of cracking of the sputtering target material can be solved by reducing the size of the voids to not more than a predetermined size per unit area and by reducing the number of voids to not more than a predetermined value.

That is, with respect to the entirety of the sputtering target material, the metal component of the present invention, the Sn 20 atom% to 50 atom%, and the oxide-sintered body containing Zn of 50 atom% to 80 atom%, exceeding, per 1050㎛ ² 2.0㎛ Less than one pore with a circle equivalent diameter.

It is also preferable that the sputtering target material of the present invention has five or less pores having a circle-equivalent diameter of 0.1 to 2.0 μm per 1050 μm ² .

The sputtering target material of the present invention preferably has an average value of relative density of 98.5% or more. It is more preferable that the deviation of the relative density from the average value is 0.3% or less.

The sputtering target material of the present invention can suppress cracking that occurs during handling such as reversing work during machining or bonding. Thus, the present invention is a technique useful for forming a channel layer of a TFT in a manufacturing process of a large liquid crystal display, an organic EL display, or the like.

1 is an electron micrograph of a sputtering target material of Inventive Example 1. Fig.
2 is an electron micrograph of a sputtering target material of Inventive Example 2;
3 is an electron micrograph of a sputtering target material of Inventive Example 3;
4 is an electron micrograph of a sputtering target material of the fourth embodiment of the present invention.
5 is an electron micrograph of a sputtering target material of Inventive Example 5;
6 is an electron micrograph of a sputtering target material of a comparative example.
Fig. 7 is a diagram showing an example of a density measurement region of the sputtering target material. Fig.

The sputtering target material of the present invention has less than one void having a circle equivalent diameter exceeding 2.0 mu m per unit area of 1050 mu m < ^{2 &} gt ;. As described above, the sputtering target material is usually processed into a predetermined shape by machining and used. Here, in the machining, the grinding with the diamond grindstone is carried out. At this time, the sputtering target material is subjected to high load such as compression and shearing due to grinding.

In addition, even when the sputtering target material is handled by a transportation operation or a reversing operation in the bonding step, only a part of the sputtering target material is supported, and most of the sputtering target material is subjected to high load such as bending because most of the sputtering target material works without support.

The sputtering target material of the present invention has a number of voids each having a circle equivalent diameter exceeding 2.0 占 퐉 per 1050 占 퐉 ² and less than one void so that even if a high load such as compression, shearing and bending is applied, Propagation of cracking in the sputtering target material itself can be suppressed and breakage of the sputtering target material itself can be prevented.

In the sputtering target material of the present invention, in order to improve crack resistance, it is preferable that the number of voids having a circle equivalent diameter of not less than 0.1 μm and not more than 2.0 μm per 1050 μm ² is not more than 5.

Here, in the present invention, the circle-equivalent diameter of the public is obtained by photographing a hole displayed in black on the reflection electron image by a scanning electron microscope in any three visual fields on the sputtering surface of the sputtering target material, (For example, " Scandium " manufactured by OLYMPUS SOFT IMAGING SOLUTIONS GMBH).

The sputtering target material of the present invention is an oxide sintered body containing 20 atom% to 50 atom% of Sn and 50 atom% to 80 atom% of Zn with respect to the whole metal component. In the present invention, by setting the amount of Sn to 20 atomic% or more, it is possible to reduce the ratio of Zn, that is, ZnO, to suppress the vacancies caused by evaporation of ZnO, and to improve the density of the sputtering target material. On the other hand, by setting the amount of Sn to 50 atomic% or less, the excess of SnO ₂ can be suppressed, the sintering property can be improved, and the density of the sputtering target material can be improved. The amount of Sn is preferably 20 atom% to 40 atom%, more preferably 25 atom% to 35 atom%.

Further, in the present invention, the Zn amount of not less than 50 atomic%, the proportion of Sn that is by reducing the SnO _2, SnO is ₂ may have to be suppressed from being excessive and to improve the sintering property and to improve the density of material sputtering target. On the other hand, by setting the amount of Zn to 80 atomic% or less, voids generated by evaporation of ZnO having a high vapor pressure can be suppressed and the density of the sputtering target material can be improved. The amount of Zn is preferably 60 atom% to 80 atom%, more preferably 65 atom% to 75 atom%.

The sputtering target material of the present invention is a sputtering target material in which a part of Zn is at least one of Al, Si, Ga, Mo and W in a total amount of 0.005 atom% to 4.000 atom% . ≪ / RTI > Of these elements, Al, Ga, Mo, and W are useful elements for preventing the control of the mobility of carriers and the deterioration of light. Further, Si is an element useful for improving the sinterability.

Further, in the sputtering target material of the present invention, the remainder other than the above-mentioned metal component is composed of oxygen and inevitable impurities. The content of the inevitable impurities of the sputtering target material of the present invention is preferably small and may include inevitable impurities such as nitrogen and carbon within a range not impairing the function of the present invention.

The sputtering target material of the present invention preferably has an average value of relative density of 98.5% or more. Thus, by suppressing the occurrence of an abnormal discharge during sputtering and obtaining a stable discharge, it is possible to improve the film quality of the ZTO thin film to be formed, and to suppress the generation of nodules. Further, in the present invention, from the viewpoint of improving crack resistance of the sputtering target material, it is more preferable that the relative density exceeds 99.0%.

In the sputtering target material of the present invention, the deviation from the average value of the relative density is more preferably 0.3% or less. This makes it possible to suppress the occurrence of breakage or cutting during machining of the sputtering target material.

The relative density of the sputtering target material in the present invention means the value obtained by dividing the bulk density of the sputtering target material measured by the Archimedes method by the theoretical density in percentage. Here, the theoretical density is a value obtained as a weighted average calculated from the mass ratio obtained from the composition ratio.

7, a portion (i to iv) corresponding to the outer periphery of the obtained sputtering target material and a portion (v) corresponding to the central portion are formed on the surface of the sputtering target material, In total. In the case of a rectangular sputtering target material such as a rectangular shape, the total number of the four spots corresponding to the corner portions of the obtained sputtering target material and the portion corresponding to the center portion are five spots in total. In the present invention, an average value of these five relative density values is adopted.

Hereinafter, an example of a method for producing the sputtering target material of the present invention will be described.

The sputtering target material of the present invention can be obtained by mixing ZnO powder and SnO ₂ powder with pure water and a dispersing agent to prepare a slurry, drying the slurry, preparing granulated powder, calcining the granulated powder, ₂ SnO ₄ ). Then, the calcined powder is wet-cracked, the formed body is formed by injection molding, and the resulting body is degreased and fired in an air atmosphere at normal pressure.

The calcining temperature of the granulated powder for producing the calcined powder is preferably set at 1000 to 1200 캜. By the calcination temperature above 1000 ℃, it is possible to sufficiently proceed the reaction of the ZnO powder and the SnO ₂ powder. On the other hand, by setting the calcination temperature at 1200 占 폚 or lower, it is possible to maintain an appropriate powder particle size, thereby obtaining a dense sputtering target material.

The firing temperature in the air atmosphere is preferably set at 1300 to 1500 ° C. By setting the firing temperature at 1300 占 폚 or higher, sintering can be promoted and a dense sputtering target material can be obtained. By using a dense sputtering target material, cracking can be suppressed even under a high load. Also, as this dense sputtering target material, a sputtering target material having less than one hole having a circle equivalent diameter exceeding 2.0 占 퐉 per 1050 占 퐉 ² can be obtained. On the other hand, when the firing temperature is 1500 캜 or lower, the evaporation of the ZnO powder can be suppressed, and a dense sputtering target material can be obtained.

The sputtering target material of the present invention can also be obtained by press-sintering the granulated powder produced by crushing, granulating and degreasing the calcined powder obtained by the same method as described above. Examples of the means for pressurizing and sintering include hot press, discharge plasma sintering, hot isostatic pressing and the like. Among them, the hot press and the discharge plasma sintering are preferable because the residual stress of the sintered body can be reduced and cracking of the sputtering target material can be prevented.

The sintering temperature in the pressure sintering is preferably set to 900 to 1100 캜. By setting the sintering temperature at 900 占 폚 or higher, sintering can be promoted and a dense sputtering target material can be obtained. By using a dense sputtering target material, cracking can be suppressed even under a high load. Further, as the dense sputtering target material, a dense sputtering target material having less than one hole having a circle equivalent diameter exceeding 2.0 占 퐉 per 1050 占 퐉 ² can be obtained. On the other hand, when the sintering temperature is lower than or equal to 1100 ° C, evaporation of the ZnO powder can be suppressed, and the reduction reaction in which the SnO ₂ powder reacts with the pressure-sintering member can be suppressed.

The pressing force of the pressure sintering is preferably set to 20 to 40 MPa. By setting the pressing force to 20 MPa or more, it is possible to obtain a dense sputtering target material having less than one void having a circle equivalent diameter exceeding 2.0 占 퐉 per 1050 占 퐉 ² . On the other hand, by setting the pressing force to 40 MPa or less, cracking of the pressure-sintering member and occurrence of breakage of the resulting sputtering target material can be suppressed.

The sintering time of the pressure sintering is preferably set to 3 to 15 hours. By setting the sintering time to 3 hours or more, it is possible to sufficiently advance the sintering and obtain a dense sputtering target material having less than one pore having a circle equivalent diameter exceeding 2.0 占 퐉 per 1050 占 퐉 ² . On the other hand, by setting the sintering time to 15 hours or less, it is possible to suppress a decrease in production efficiency.

<Examples>

First, a ZnO powder having an average particle diameter (D50 of cumulative particle size distribution) of 0.70 占 퐉 and an average particle diameter (D50 of cumulative particle size distribution) of 1.85 Mu m of SnO ₂ powder was weighed and placed in a stirring vessel containing a predetermined amount of pure water and a dispersing agent and mixed to prepare a slurry. This slurry was dried and then subjected to crushing, granulation and degreasing to obtain granules having an average particle diameter (D50 of cumulative particle size distribution) of 45 μm.

Subsequently, the granulated powder obtained above was prebaked at 1090 DEG C to obtain calcined powder. The calcined powder was wet-cracked, and the obtained slurry was injection-molded to produce three molded bodies.

Then, one of the obtained compacts was subjected to atmospheric pressure baking at 1400 DEG C for 10 hours in an atmospheric atmosphere, and further heat-treated at 1400 DEG C for 10 hours in a nitrogen reducing atmosphere to obtain a sintered body.

The obtained sintered body was subjected to planar grinding using a diamond grinding stone, and then a sputtering target material having a thickness of 10 mm and an outer diameter of 100 mm was produced using a water jet cutter.

Further, one of the compacts obtained above was subjected to atmospheric pressure firing under the conditions of 1400 DEG C for 5 hours and an air atmosphere, and further heat-treated at 1400 DEG C for 12 hours in a nitrogen reducing atmosphere to obtain a sintered body.

The obtained sintered body was subjected to plate thickness processing by planar grinding using a diamond grinding stone, and then a sputtering target material having a thickness of 10 mm and an outer diameter of 100 mm was produced by using a water jet cutter.

Further, one of the compacts obtained above was sintered at 1400 DEG C for 5 hours under atmospheric pressure to obtain a sintered body. This sintered body was subjected to plate thickness processing by planar grinding using a diamond grinding stone, and then a sputtering target material of the present invention 3 having a thickness of 10 mm and an outer diameter of 100 mm was produced by using a water jet cutter.

The calcined powder obtained above was charged into a pressurized vessel made of carbon, placed in a furnace body of a discharge plasma sintering apparatus, and subjected to pressure sintering under the conditions of 950 DEG C and 40 MPa for 12 hours. After pressure sintering, And then removed from the pressure vessel to obtain a sintered body.

The resulting sintered body was subjected to plate thickness processing by planar grinding using a diamond grinding stone, and then a sputtering target material having a thickness of 10 mm and an outer diameter of 100 mm was produced using a water jet cutter.

The calcined powder obtained above was charged into a pressurized vessel made of carbon, placed inside the furnace body of the hot press apparatus, and subjected to pressure sintering under the conditions of 970 DEG C and 20 MPa for 12 hours.

The obtained sintered body was subjected to plate thickness processing by planar grinding using a diamond grinding stone, and then a sputtering target material having a thickness of 10 mm and an outer diameter of 100 mm was produced using a water jet cutter.

As a comparative example, a sputtering target material was produced as follows. First, a ZnO powder having an average particle diameter (D50 of cumulative particle size distribution) of 0.70 占 퐉 and an average particle diameter (D50 of cumulative particle size distribution) of 1.85 Mu m of SnO ₂ powder was weighed and placed in a stirring vessel containing a predetermined amount of pure water and a dispersing agent and mixed to prepare a slurry. This slurry was dried and then subjected to crushing, granulation and degreasing to obtain granules having an average particle diameter (D50 of cumulative particle size distribution) of 45 μm. This granulated powder was subjected to wet cracking, and the obtained slurry was injection-molded to prepare a molded article.

Subsequently, the obtained molded body was subjected to normal pressure firing at 1550 DEG C for 4 hours.

The resulting sintered body was subjected to plate thickness processing by planar grinding using a diamond grinding stone, and then a sputtering target material having a thickness of 10 mm and an outer diameter of 100 mm was manufactured using a water jet cutter.

A 10 mm x 10 mm x 10 mm specimen for electron microscope observation was cut out from each of the sintered bodies obtained above, and the surface of the specimen was subjected to mirror polishing and then observed. Then, the surface of each sintered body was observed on a reflecting electron of a scanning electron microscope for a visual field of 1050 mu m &lt; ² &gt; in an arbitrary field of view at 3 o'clock and the presence or absence of a hole existing in each field of view, And the number of pores exceeding 2.0 占 퐉 and the number of pores having a range of 0.1 占 퐉 to 2.0 占 퐉 were measured.

Table 1 and from the results of Figs. 1 to 5, by observing the unit area is called a random 1050㎛ ² sputtering target material of the invention, the public that the circle-equivalent diameter of matter in which field of view exceeds that there is 2.0㎛ I could confirm. It was also confirmed that the number of holes having a circle-equivalent diameter of 0.1 mu m or more and 2.0 mu m or less was 5 or less even in the field of view with the greatest number of holes.

Then, a sputtering test was carried out using the ZTO sputtering target material of the present invention example. Sputtering was carried out under the conditions of an Ar atmosphere, a pressure of 0.5 Pa, and a DC power of 300 W for an integration time of 4 hours. Further, in order to evaluate the sputtering target itself, the sputtering test was performed in an Ar atmosphere instead of reactive sputtering.

When the sputtering target material of the present invention after the sputtering test was visually inspected, no occurrence of cracking was confirmed in any of the sputtering target materials.

On the other hand, as shown in the comparative example a sputtering target material, Fig. 6, when observing the unit area is called a random 1050㎛ ² 1 field, the public that the circle equivalent diameter exceeds 2.0㎛ existed three or.

Then, a sputtering test was carried out under the same conditions as above using the sputtering target material of the comparative example. When the sputtering target material as a comparative example after the sputtering test was visually inspected, it was confirmed that four cracks occurred in the radiation image from the substantially central portion of the surface of the sputtering target material.

From each of the sintered bodies obtained above, analytical samples each having a size of 10 mm x 20 mm x 20 mm were cut out from the measurement sites shown in Fig. 7, and the true density of each site was measured. The relative density was calculated by the above- Respectively. The results are shown in Tables 2 and 3.

From the results shown in Tables 2 and 3, the density of the sputtering target material of the present invention was measured at five sites, namely, regions (i to iv) corresponding to the outer peripheral portion and region (v) corresponding to the central portion. Relative density was more than 98.5%. It was also confirmed that the deviation from the average value of the relative density was 0.3% or less. In Inventive Example 1 and Inventive Example 4, the average value of the relative density exceeded 99.0%, and a sputtering target material having a high relative density could be obtained.

On the other hand, in the sputtering target material of the comparative example, the density measurement was performed at five points of the portion (i to iv) corresponding to the outer peripheral portion and the portion (v) corresponding to the central portion. Also, the deviation from the average value of the relative density was 0.7% at the maximum, which was larger than the deviation of the sputtering target material of the present invention.

1: Zn ₂ SnO ₄ phase
2: ZnO phase
3: Public

Claims (4)

Wherein the oxide sintered body contains 20 atom% to 50 atom% of Sn and 50 atom% to 80 atom% of Zn with respect to the whole metal component, and one pore having a circle equivalent diameter exceeding 2.0 탆 per 1050 탆 ² , &Lt; / RTI &gt; The sputtering target material according to claim 1, wherein the number of voids having a circle-equivalent diameter of not less than 0.1 μm and not more than 2.0 μm per 1050 μm ² is not more than 5. The sputtering target material according to claim 1 or 2, wherein an average value of the relative density is 98.5% or more. 4. The sputtering target material according to claim 3, wherein the deviation [(maximum value - minimum value) / average value x 100 (%)] from the average value of the relative density is 0.3% or less.

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