KR20090049321A - Method of fabricating a sputtering target of zns composite and sputtering target of zns composite prepared thereby - Google Patents

Abstract

The present invention relates to a method for producing a ZnS-based sputtering target and to a ZnS-based sputtering target thus obtained, and more particularly, to a method for producing a ZnS-based sputtering target by subjecting ZnS alone or ZnS-SiO ₂ mixed powder to discharge plasma sintering It relates to a ZnS-based sputtering target thus obtained.

The prepared sputtering target has a density of 99% or more, fine grains, and excellent mechanical properties, and has an advantage of greatly shortening a manufacturing process time by performing a discharge plasma sintering process.

Sputtering Target, Discharge Plasma Sintering, Fine Grain

Description

METHOD OF FABRICATING A SPUTTERING TARGET OF ZnS COMPOSITE AND SPUTTERING TARGET OF ZnS COMPOSITE PREPARED THEREBY}

The present invention provides a method for producing a ZnS-based sputtering target having a density of 99% or more, fine grains, excellent mechanical properties, and greatly shortening a manufacturing process time by performing a discharge plasma sintering process, and the resulting ZnS-based sputtering target. It relates to a sputtering target.

ZnS-SiO _2, which is widely used as a protective film for optical recording media, is manufactured in a thin film form through sputtering.

In recent years, productivity improvement by increasing demand of optical recording media is required, and therefore, the deposition rate of a component layer needs to be speeded up, and the use of high output sputtering has become common. The use of such a high power sputter has a problem of shortening the life by causing cracking of the target material.

Therefore, in order to improve the mechanical properties of the final product, the composite material is prepared by adding a secondary phase material, or sintered using a ZnS single phase or a composite powder having a secondary phase milled to give an excellent microstructure. Rather, there is a problem that the sinterability is lowered.

Meanwhile, ZnS or ZnS-SiO ₂ sputtering targets used to prepare ZnS-SiO ₂ thin films are generally manufactured by hot compression.

The hot compression method is a method of improving the sinterability by simply heating the material and simultaneously applying pressure. For example, a ZnS sputtering target is manufactured by sintering at a pressure of 30 to 98 MPa in a temperature range of 900 to 1200 ° C., or ZnS-SiO _{2 The} mixed powder is prepared by sintering for 6 hours at 31150 MPa pressure at 1150 ℃.

However, in order to obtain a high-density sintered body by the hot compression method, a long sintering time is required, which causes the growth of matrix particles of the known phase and the secondary phase and causes a problem that the mechanical properties of the sintered body are greatly reduced.

Recently, the discharge plasma sintering process that enables instant heating using the discharge plasma by the energizing pressure method using the DC pulse has been in the spotlight.

Accordingly, the present inventors have variously studied to provide a ZnS-based sputtering target having better physical properties compared to the sputtering target obtained by the hot compression method by establishing the process conditions when manufacturing the ZnS-based sputtering target using the discharge plasma sintering process. Was performed.

An object of the present invention relates to a method for producing a ZnS-based sputtering target having a density and fine grains of 99% or more, excellent mechanical properties, and can shorten the manufacturing process time.

In order to achieve the above object, the present invention

ZnS alone or ZnS-SiO ₂ mixed powder to perform a discharge plasma sintering process to provide a method for producing a ZnS-based sputtering target.

In another aspect, the present invention provides a ZnS-based sputtering target prepared by the above method.

The discharge plasma sintering process according to the present invention can be performed in a short time compared to the conventional hot compression method, it is possible to manufacture a high-density sintered compact crystal grains, it is possible to manufacture a sputtering target with improved mechanical properties.

Hereinafter, the present invention will be described in more detail.

Spark Plasma Sintering is an effective method for densifying ceramic or metal materials in a short time by facilitating mass transfer between powder particles by applying a high current to the raw powder and applying a high current to generate plasma between the powders. Luan W, Gao L, Kawaoka H, Sekino T, Niihara K, Fabrication and characteristics of fine-grained BaTiO ₃ ceramics by spark plasma sintering, Ceram Int 2004; 30: 405-410]

Accordingly, in the present invention, the sputtering target of the sintered compact is manufactured by performing a discharge plasma sintering process on the ZnS-based raw material powder.

The ZnS-based raw material powder may be ZnS alone or ZnS-SiO ₂ mixed powder. At this time, ZnS and SiO ₂ used are finer particles through a subsequent ball mill process, so the size is not necessary to limit, in the embodiment of the present invention is the average particle size of 5 ㎛, in the case of SiO ₂ powder of the size of 10 ㎛ use.

The ZnS-based raw material powders all contain a β-ZnS phase.

In particular, the ZnS-SiO ₂ mixed powder is prepared by injecting ZnS and SiO ₂ raw powder into a ball and a ball mill, followed by ball milling under a wet medium.

At this time, the ZnS and SiO ₂ raw powder are mixed in a molar ratio of 6: 1 to 2: 1, respectively. If the content of SiO ₂ is less than the above range, it does not contribute to the improvement of the mechanical properties of the target. On the contrary, if the content exceeds the above range, it is not preferable because it inhibits the thin film properties when depositing the thin film with the target.

The ball is not particularly limited in the present invention, a known stainless steel ball, alumina ball or zirconium ball is used, wherein the ball is a raw material powder and a loading ratio (weight ratio) of 14: 1 to 18: 1, preferably The ball mill is performed smoothly by mixing in a weight ratio of 16: 1.

The wet medium may be an alcohol comprising ethanol.

At this time, the ball mill apparatus that can be used is not particularly limited in the present invention, typically an attritor, a 3-D mixer, a planetary ball mill, a vibratory ball mill, a horizontal ball mill Various ball mill devices such as ball-mills are possible.

The raw material powder is carried out in the above-described ball mill apparatus at a speed of 50 to 500 rpm, preferably 100 to 500 rpm for 1 to 20 hours, and the mixed powder obtained after the ball mill process is 12 to 36 hours at a temperature of 40 to 80 ° C. It is prepared by drying during the process to sufficiently remove the alcohol medium. The conditions in the ball mill process are to sufficiently finely and uniformly mix the particles of ZnS and SiO ₂ , and if the ball mill process is performed out of the above-described range, the sintered compact obtained after the subsequent discharge plasma sintering process Deterioration of physical properties is caused.

The ZnS-SiO ₂ mixed powder thus prepared was confirmed to coexist with α-ZnS phase and β-ZnS phase as a result of phase analysis by XRD.

A ZnS-based sintered compact is manufactured by performing a discharge plasma sintering process on the ZnS-based raw material powder as described above through a spark plasma sintering system (SPS).

The discharge plasma sintering system is not limited in the present invention, it is possible to use a device commonly used in this field, as shown in FIG.

According to FIG. 1, the discharge plasma sintering system places a graphite mold containing mixed powder in a chamber located between the upper and lower electrodes, adjusts temperature and pressure through the controller (a), and then applies DC-pulse current (b). Sintering of the mixed powder is carried out.

At this time, a graphite mold (c) having an inner diameter of 20 mm and an outer diameter of 50 mm was used, and a hole was drilled to a depth of 1.6 mm in diameter and 3 mm in length in the center of the mold, and then the temperature was measured by inserting an R-type thermocouple. .

The current flows directly into the mold and the specimen through the punch for pressing, and sintering proceeds by the generation of plasma by the heat of resistance of the specimen and the mold. The discharge plasma sintering system used in this study can apply a maximum pressure of 6 Ton and a maximum current of 3000A.

Specifically, after evacuating the chamber of the discharge plasma sintering apparatus, the raw material powder compact in the mold is heated to 700 to 1200 ° C at a heating rate of 50 to 150 ° C / min, and then sintered by applying a pressure of 30 MPa or more. .

At this time, the higher the temperature increase rate and pressure, the more advantageous in terms of particle growth and density of the sintered body, but considering the operating range of the equipment according to the current technology, the sintering pressure range of 30 to 90 MPa at a temperature increase rate of 50 to 150 ℃ / min Perform under If the sintering temperature is lower than the above, sintering is difficult and there is a possibility that a problem of lowering the density may occur. At this time, if the sintering temperature exceeds the above range ZnS may be sublimated, it is carried out within the above range.

This sintering process is carried out for 1 to 10 minutes in order to proceed with sufficient sintering.

As such, the sintering process using the discharge plasma sintering apparatus selects and performs the optimum conditions in consideration of the heating rate, the sintering temperature, the pressure and time, and various other process variables, and the optimum conditions are known in the art. It can be appropriately selected within the above range by the person having.

The discharge plasma sintering process according to the present invention as described above can be performed in a short time compared to the conventional hot compression method, the energy consumption of about 1/3 to 1/5 less than the hot press (Hot Press) method It is a saving type sintering method and has the advantage of easy handling. In addition, the running cost is low, it can reduce energy consumption and improve production speed in sputtering target manufacturing, and can be applied to products requiring high sintering density for quality stability of the final product.

The ZnS-based sintered body manufactured through the discharge plasma sintering process is a sintered body of ZnS single phase or ZnS-SiO ₂ mixed phase, and has a density and fine grains of 99% or more. In this case, the ZnS-SiO ₂ mixed phase sintered compact has a SiO ₂ particle size of 0.5 to 10 μm, preferably 0.5 to 1 μm. The ZnS-based sintered body has a significant improvement in mechanical properties such as improved fracture toughness and ductility compared to powder obtained by simple mixing or hot compression.

Specifically, according to Experimental Example 5 of the present invention, the ZnS-based sintered body has a density of 99% or more, preferably 99.47 to 99.56%, and more preferably 99.4 to 99.6%. The Vickers hardness is 2.0 GPa or more, preferably 2.2 to 3.1 GPa, more preferably 2.3 to 3.1 GPa. And a fracture toughness MPa · m ^0.5 or more has a 0.5, 0.55 to 1.02 preferably to MPa · m ^0.5, 0.8~1.02 to more preferably MPa · m ^{0. 5.}

The ZnS-based sintered body manufactured by the present invention has a dense density and excellent mechanical properties such as Vickers hardness and fracture toughness, which not only prolongs its life when used as a sputtering target but also distributes ZnS and SiO ₂ more uniformly when forming a protective layer. There is an advantage.

Especially, ZnS-stage for routine and ZnS-SiO case on the mixture of the _two this sputtering target are shown the equivalent optical properties to each other when forming a thin film or mixing a sputtering target of ZnS-SiO ₂ that contains a SiO ₂ using a There is an advantage of showing better mechanical properties.

In other words, in the case of a sputtering target, sputtering is repeatedly performed to form a thin film, in which a crack occurs in the target, which causes a shortening of the life of the sputtering target. Therefore, in the mixed phase sputtering target of ZnS-SiO ₂ prepared in the present invention, fracture toughness is increased by fine and uniformly distributed SiO ₂ , so that the propagation of cracks generated during repeated sputtering due to the effect of crack deflection Suppressed. As a result, when manufacturing the sputtering target through the discharge plasma sintering process according to the present invention it is possible to solve the problem of shortening the life of the conventional sputtering target.

The ZnS-based sintered compact is used as a sputtering target to provide various phase change type optical recording media rewritable compact discs (CD-RW), random access memory digital video discs (DVD-RAM), DVD + rewritable (DVD + RW), and the like. The same applies to the material of the protective thin film layer of the same rewritable optic disks.

Hereinafter, preferred examples are provided to aid in understanding the present invention. However, the following examples are merely provided to more easily understand the present invention, and the contents of the present invention are not limited by the examples.

Example  One: ZnS Single phase Sputtering Of target  Produce

Using pure ZnS powder (average particle size 5 μm, spherical, purity 99.99%, CERAC USA), using a discharge plasma sintering apparatus, the temperature was raised to 900 ° C. at a heating rate of 100 ° C./min, and then 5 minutes at a pressure of 30 MPa. Sintering was carried out to prepare a ZnS single phase sputtering target.

Example  2: ZnS - SiO ₂ Mixed phase Sputtering Of target  Produce

Of ZnS (80 mol.%)-SiO ₂ (20 mol.%) Using ZnS (purity 99.99%) and SiO ₂ (purity 98%, average particle size 10 μm, purity 98%, STREM CHEMICALS, USA) Weighed to the composition.

The mixed powder was simply mixed for 10 hours at a speed of 62 rpm in a 3-D mixer, and heated to 1100 ° C. at a temperature increase rate of 100 ° C./min using a discharge plasma sintering apparatus. Sintering was then performed at a pressure of 80 MPa for 5 minutes to prepare a ZnS-SiO ₂ mixed phase sputtering target.

Example  3: ZnS - SiO ₂ Mixed phase Sputtering Of target  Produce

The mixed powder was weighed in the same manner as in Example 2, followed by wet high energy ball milling in an ethanol medium for 1 hour at a speed of 400 rpm using an Attrittor. At this time, the charging ratio of the ball and the powder was 16: 1, and after ball milling, the mixture was sufficiently dried at 60 ° C. for 24 hours in an oven to prepare ZnS-SiO ₂ mixed powder.

ZnS-SiO ₂ mixed phase sputtering target was manufactured by raising the mixed powder prepared above by using a discharge plasma sintering apparatus, raising the temperature to a temperature of 100 ° C./min to 1100 ° C., and sintering at a pressure of 90 MPa for 5 minutes. .

Example 4: ZnS-SiO ₂  Preparation of Mixed Phase Sputtering Targets

In the same manner as in Example 3, but the milling was carried out for 10 hours to prepare a ZnS-SiO ₂ mixed powder, sintering for 5 minutes at a pressure of 90 MPa after raising to 1200 ℃ at a temperature increase rate of 100 ℃ / min ZnS-SiO ₂ mixed phase sputtering target was prepared.

Experimental Example 1: XRD Analysis of Raw Material Powder

XRD analysis was performed to determine the crystal structure and average grain size of the raw powder.

Figure 2 (a) is pure ZnS powder, (b) ZnS-SiO ₂ powder is simply mixed in a 4: 1 molar ratio, and (c) ZnS-SiO ₂ is 4: 1 ball for 10 hours XRD spectrum of milled mixed powder.

Referring to FIG. 2, it was confirmed that each powder was β-ZnS, and the average grain size was about 40 nm for pure ZnS and a simple mixed powder, and about 20 nm for a powder milled for 10 hours. .

Experimental Example  2: sintered body XRD  analysis

XRD analysis was performed to determine the crystal structure and average grain size of the sintered body.

(A) is pure ZnS sintered body, (b) sintered body in which ZnS-SiO ₂ is simply mixed in a molar ratio of 4: 1, and (c) is ZnS-SiO ₂ in 4: 1 molar ratio for 10 hours. XRD spectrum of the milled sintered body.

3, it can be seen that after sintering, peaks in the crystal directions of (100), (101), (102), and (103) grow, which means that some β-ZnS (cubic) phases in the powder state are α-ZnS ( It is the result of phase transformation into hexagonal), and it can be seen that the α-ZnS phase and the β-ZnS phase coexist in the sintered body.

Experimental Example  3: SEM  Photo measurement

In order to confirm the microstructure of a sintered compact, it measured by SEM of each sintered compact.

Figure 4 (a) is a SEM photograph of the sintered compact in 10, the ZnS-SiO ₂ in a molar ratio of 4: 1 in Example 2, (b) is ZnS-SiO ₂ 4: 1 in Example 3 SEM image of the mixed powder sintered body ball-milled for 1 hour at a molar ratio of (c) is SEM image of the mixed powder sintered body ball-milled for 10 hours at a molar ratio of ZnS-SiO ₂ 4: 1 in Example 4.

Referring to FIG. 4, when the ZnS-SiO ₂ was simply mixed and the microstructure of the sintered body of the ball milling powder for 1 hour and 10 hours was observed, the ball milling process was performed rather than the high energy ball milling. It exhibits a fine and uniform microstructure characteristic, which is based on the result of particle refinement of secondary phase SiO ₂ with milling time.

Experimental Example 4: Checking Crack Mechanism

The microstructure of each sintered body was measured by OM and SEM to identify the mechanism that prevents the propagation of cracks generated at the tip of Micro Vickers' indentor.

5A is an OM photograph of a ZnS sintered body, (b) is an OM photograph of a powder sintered body mixed with ZnS-SiO ₂ at a molar ratio of 4: 1 for 10 hours, and (c) is ZnS-SiO ₂ valent SEM photographs of the mixed powder sinters ball milled for 10 hours at a molar ratio of 4: 1, showing the mechanism of crack propagation in each sinter.

Referring to FIG. 5, a crack deflection phenomenon occurs in which the crack generated at the tip of the indenter is bent around the secondary dispersion phase SiO ₂ used in the present experiment. The crack deflection phenomenon is directly related to the fracture toughness, and this result suggests that the fracture toughness of the sputtering target can be improved when the ball milling is performed for 10 hours.

Experimental Example 5: Measurement of Physical Properties

The physical properties of the sintered bodies prepared in Examples 1, 3 and 4 and the sputtering targets (commercially available) prepared by conventional hot compression molding as a control example were measured, and the results are shown in Table 1 below.

Density measurement

Density measurement was measured by the Archimedes method (Archimedes' principle), it is shown in Table 1 compared with the results of each condition and the relative density of the commercial target produced by the hot compression molding method.

Hardness Measurement and Fracture Toughness Measurement

The hardness of the prepared sintered compact was simply specified by the Micro Vickers' indentation method, and fracture toughness was calculated by the indentation fracture method represented by Equation 1 below.

[Equation 1]

(In Equation 1, K _IC is fracture toughness, a is 1/2 of the diagonal length of the indenter, c is the length from the center of the indenter to the end of the crack, the formula applies only when c / a is 2.5 or more)

Manufacture process Relative Density (%) Vickers Hardness (GPa) Fracture Toughness (K _IC , MPam ^0.5 ) Example 1: Pure ZnS Sintered Body SPS 99.47% 2.222 0.572 Example 2: ZnS-SiO ₂ Sintered Body SPS 99.48% 2.371 0.805 Example 4: ZnS-SiO ₂ Sintered Body SPS 99.56% 3.031 1.014 Control Example: (ZnS-SiO ₂ ) Hot compression process 94.89% 1.928 0.594

Referring to Table 1, it can be seen that compared with (ZnS-SiO ₂ ) manufactured by the hot compression process, the sintered body manufactured by the discharge plasma sintering process according to the present invention is excellent in relative density, hardness and fracture toughness. Can be. In particular, the sintered compact of Example 4, which performed the ball mill process for 10 hours, showed the best results.

1 is a schematic diagram showing a discharge plasma sintering system according to an embodiment.

Figure 2 (a) is pure ZnS powder, (b) ZnS-SiO ₂ powder is simply mixed in a 4: 1 molar ratio, and (c) ZnS-SiO ₂ is 4: 1 ball for 10 hours XRD spectrum of the milled mixed powder.

(A) is pure ZnS sintered body, (b) sintered body in which ZnS-SiO ₂ is simply mixed in a molar ratio of 4: 1, and (c) is ZnS-SiO ₂ in 4: 1 molar ratio for 10 hours. XRD spectrum of the milled sintered body.

Figure 4 (a) is a SEM photograph of the sintered compact in 10, the ZnS-SiO ₂ in a molar ratio of 4: 1 in Example 2, (b) is ZnS-SiO ₂ 4: 1 in Example 3 SEM image of the mixed powder sintered body ball-milled for 1 hour at a molar ratio of (c) is SEM image of the mixed powder sintered body ball-milled for 10 hours at a molar ratio of ZnS-SiO ₂ 4: 1 in Example 4.

5A is an OM photograph of a ZnS sintered body, (b) is an OM photograph of a powder sintered body mixed with ZnS-SiO ₂ at a molar ratio of 4: 1 for 10 hours, and (c) is ZnS-SiO ₂ valent It is a SEM photograph of the mixed powder sintered compact ball-milled for 10 hours at 4: 1 molar ratio.

Claims (9)

Method for manufacturing a ZnS-based sputtering target by performing a discharge plasma sintering process of ZnS alone or ZnS-SiO ₂ mixed powder The method of claim 1, The ZnS-SiO ₂ mixed powder is prepared by injecting ZnS and SiO ₂ raw material powder into a ball and ball mill apparatus and then ball milling under a wet medium. The method of claim 2, The ZnS and SiO ₂ raw material powder is a method for producing a ZnS-based sputtering target is mixed in a molar ratio of 6: 1 to 2: 1, respectively. The method of claim 2, The ball milling is a method for producing a ZnS-based sputtering target that is performed for 1 to 20 hours at a speed of 100 to 500 rpm. The method of claim 1, The discharge plasma sintering is a ZnS system in which ZnS alone or ZnS-SiO ₂ mixed powder is heated to 700-1200 ° C. at a heating rate of 50-150 ° C./min, and then sintered by applying a pressure of 30-90 MPa. Method for producing a sputtering target. A ZnS-based sputtering target produced by the method according to any one of claims 1 to 5. The method of claim 6, The sputtering target of the ZnS-based sputtering target is a ZnS single phase or ZnS-SiO ₂ mixed phase. The method of claim 6, The ZnS-based sputtering target has a SiO ₂ particle size of 0.5 to 10 μm, a density of 99% or more, a Vickers hardness of 2.0 GPa or more, and a fracture toughness of 0.5 MPa · m ^0.5 or more. The method of claim 6, The ZnS-based sputtering target is a particle size of 0.5~1 ㎛, a density of 99.47~99.56%, and the Vickers hardness is 2.2~3.1 GPa, fracture toughness is 0.55~1.02 MPa · m ^{0. 5} in that the ZnS-based sputtering target.

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