KR20080102786A - Zinc oxide-based sputtering target manufacturing method using spark plasma sintering - Google Patents

Abstract

A zinc oxide-based sputtering target manufacturing method using spark plasma sintering having high intensity is provided to achieve high intensity and excellent property by mixing and drying the zinc oxide powder and using the spark plasma sintering. The zinc oxide powder is pulverized and dried(S1). The carbon sheet is mounted to the mold for the electric discharge plasma sintering filling the powder(S2). A mold set is prepared by filling the power in the mold in which the carbon sheet is mounted, and sets the powder at a chamber of a spark plasma sintering system. The pressure of the chamber is reduced by an atmosphere control system. The pressure and current is given to the chamber for increasing the temperature(S4). The chamber where temperature increases is pressurized to the final sintering temperature with 10-15 mins and performs furnace cooling(S5). The carbon sheet adhering to the cooled sintered body is removed(S6).

Description

Zinc oxide-based sputtering target manufacturing method using spark plasma sintering}

 1 is an overall flowchart of a method of manufacturing a zinc oxide-based sputtering target using a discharge plasma sintering method.

 2 is an image showing a discharge plasma sintering apparatus.

 * Name of each part of drawing

 1: Processed Powder 7: Vacuum Chamber

 2: Sintering die 8: SPS DC power supply

 3: upper punch electrode 9: pressurizing device

 4: lower punch electrode 10: SPS controller

 5: upper punch 11: atmosphere control mechanism, etc.

 6: lower punch

 The present invention relates to a method for manufacturing a zinc oxide sputtering target that can replace the conventional ITO target for transparent conductive films, and in particular to oxidize using a new sintering method, the discharge plasma sintering method to achieve a high density that could not be solved in the conventional sintering method The manufacturing method which manufactures a zinc sputtering target material is related.

Recently, as interest in displays increases, development of flat panel displays (FPDs), such as thin and light liquid crystal displays (LCDs), plasma display panels (PDPs), organic light emitting diodes (OLEDs), and the like, is actively increasing.

Indium oxide (ITO) containing tin, which can realize low resistance, is the most widely used transparent conductive film that plays an important role in flat panel displays. However, as the demand for flat panel displays increases, the price of ITO targets used for transparent conductive film deposition is increasing because the supply of indium, a rare element, does not meet the demand, and the depletion of indium, which has limited resources, is expected. The demand is growing. Thus, materials that add other elements to zinc oxide are being studied as the most potent ITO alternatives.

Conventional zinc oxide (ZnO) -based sputtering target material manufacturing method is a cold hydrostatic pressing (CIP: Cold Isossatatic Pressing) by wet mixing the oxide powder or preparing a coprecipitation powder containing two or more components And then sintered in the atmosphere or inert gas atmosphere. When the zinc oxide-based sputtering target is manufactured by these methods, volatilization of zinc oxide occurs on the surface when sintered at a high temperature of 1300 ° C. or higher, and sufficient grain growth does not occur, making it impossible to obtain a sintered body having a relative density of 95% or more. In addition, when sintering is performed at a sintering temperature of 1400 ° C. or higher, closed pores are formed by melting of grain boundaries during sintering, and thus, densification is difficult, and gas contained in such pores is exposed when sputtering, thereby causing dispersion of resistance.

The present invention provides a method for producing a zinc oxide-based sputtering target using the discharge plasma sintering method as a countermeasure against the above problems.

Spark plasma sintering (SPS) is a method of directly injecting pulsed electrical energy into the gap between particles of a green compact, and rapidly dissipating high energy of a discharge plasma generated by spark discharge by thermal diffusion and electric field. It is an effective application process. Since rapid temperature rising is possible, the growth of particles can be controlled, a compact sintered body can be obtained in a short time, and an sintered material can be easily sintered.

The sintering methods up to now have been difficult to sinter, for example, ceramic composite materials such as ZrO ₂ and Al ₂ O ₃ including polymer whiskers and fibers, sintering of metallic composite materials (MMC) and high temperature sintering. It is advantageous in that it can be applied to amorphous materials that are easily crystallized and lose their properties.

In the present invention, the zinc oxide-based powder is mixed, dried, and pulverized, and thus the manufacturing method is simple using the above-described discharge plasma sintering method, and the volatilization of zinc oxide is suppressed by the pressure applied during sintering and high density close to theoretical density is achieved. It is an object of the present invention to provide a method for producing a zinc oxide-based sputtering target having excellent physical properties.

The present invention consists of preparing a zinc oxide powder and then filling the mold to produce a sintered compact as a final target by the discharge plasma sintering method. As described above, the production of zinc oxide-based sputtering targets by the conventional method has problems of volatilization of zinc oxide and suppression of density improvement by closed pore generation by grain boundary melting.

However, the composition of the present invention is a simple manufacturing method using a plasma sintering method by mixing, drying and grinding the zinc oxide powder, volatilization of zinc oxide is suppressed by the pressure applied during sintering and has a high density close to the theoretical density In addition, it is an object to provide a method for producing a zinc oxide-based sputtering target having excellent physical properties.

The structure of the discharge plasma sintering apparatus used for this invention is demonstrated with reference to FIG.

The discharge plasma sintering apparatus is composed of a pressurizing mechanism device 9, an SPS direct current power supply device 8, a vacuum chamber 7, a SPS control device 10, an atmosphere control device, etc. 11 on one vertical axis. The sintering die 2 and the upper and lower punches 5 and 6 filled with the powder to be processed 1 are set on the sintering stage in the vacuum chamber 7 and inserted into the upper and lower punch electrodes 3 and 4, When pulse energization is carried out while pressurizing, the temperature is rapidly increased to 1000 to 2500 ° C at a time rather than normal temperature within minutes to obtain a high density sintered body in a short time.

The present invention is the grinding and drying step of the zinc oxide powder by the zinc oxide-based sputtering target manufacturing method using the discharge plasma sintering method;

Mounting a carbon sheet on a mold for discharging the plasma to fill the powder;

After filling the powder, which has been subjected to the pulverization and drying step, into the mold on which the carbon sheet is mounted, preparing a mold set and setting it in a discharge plasma sintering apparatus chamber;

A discharge plasma sintering step of depressurizing the chamber by an atmosphere control mechanism and then applying a pressure and heating the same by applying a current;

Cooling the furnace in a furnace after pressurizing and maintaining 5 to 10 minutes in the elevated temperature near the final sintering temperature;

And removing the carbon sheet fixed to the cooled sintered body.

The zinc oxide powder is characterized in that a compound containing at least one element of Al, Ti, Ga, B, Mg, Ni, Si, Sn, Ta, Ba, Y is added to the zinc oxide.

At this time, the added element is substituted in the zinc position of the zinc oxide during sintering to emit electrons by the difference in the number of oxides, thereby lowering the resistance of the zinc oxide-based sintered body.

The pressure applied in the discharge plasma sintering step is 20 ~ 80MPa, the temperature increase rate is characterized in that in the range of 50 ~ 400 ℃ / min. The discharge plasma sintering step is characterized in that carried out in a vacuum atmosphere or inert gas atmosphere (Ar, N ₂ ).

 Hereinafter, a method of manufacturing a zinc oxide target according to the present invention will be described in detail with reference to FIG. 1.

First, the zinc oxide powder is pulverized and dried (S1). Grinding is performed through a ball mill, an attritor, a planetary mill, etc., which are generally performed, and water and the like are removed by drying at 200 ° C. or less for 1 hour. Since this process may not be uniform in size or shape of the powder prepared initially, to prepare a fine and uniform powder through grinding and drying, and to maintain the same conditions even during the sintering of the discharge plasma to be a post-process to be.

Mounting the carbon sheet in the discharge plasma sintering mold to fill the powder after the grinding and drying step (S2). Inside the mold, a carbon sheet having a thickness of about 0.2 mm, which is generally available, is used to fit the inside of the mold. The carbon sheet is installed to avoid contact with the powder, upper and lower punches (5, 6) and the sintering die during the sintering of the discharge plasma. When the carbon sheet is not used, it is applied to the high load and current applied during the sintering of the discharge plasma. As a result, a problem arises in that the mold and the sintered body are fixed by rising to a high temperature, and in the case of separating the mold, the mold may be expensive.

In the case where the carbon sheet is used, it is easy to separate the sintered body to which the carbon sheet is fixed and the mold, and the carbon sheet is removed by polishing, so that a healthy sintered body can be obtained simply. When the sintering temperature is higher, even when the carbon sheet is used, a reaction may occur between the mold and the sintered body. In this case, the reaction may be suppressed by additionally using ultra high temperature BN.

After the grinding and drying the powder is filled in the mold to prepare a mold set and set in the discharge plasma sintering apparatus chamber (S3). After preparing the mold set, the heights of the upper and lower punches 5 and 6 which come out of the sintering die 2 should be adjusted to the same level, in order to prevent damage to the mold due to the load biased to one side during the discharge plasma sintering. Also, when setting inside the discharge plasma sintering apparatus, the mold should be protected by adjusting the set to be in the center of the electrode. Setting means placing the prepared mold set in the center of the upper electrode and the lower electrode in the chamber, and all the work of the decompression lamp, such as thermocouple mounting and application of the target load.

The set chamber is depressurized by an atmosphere control mechanism and then pressurized by a pressurization mechanism device to increase the temperature by inputting current through a DC power supply device (S4). In the present invention, the pressure was reduced by using a vacuum device such as a rotary pump (RP), a booster pump (BP) and a diffusion pump (DP), which are atmosphere control mechanisms. The only mold that maintains high strength is a high-density carbon mold, and the atmosphere for using the mold should be a vacuum atmosphere or a gas atmosphere. Of course, the present invention is also possible in an inert gas atmosphere (Ar, N _2, etc.).

When the pressure is reduced to a certain level, it is preferable to apply a load and raise the current by raising the current at the same width for a predetermined time. At this time, the pressure applied through the pressure mechanism device (hydraulic device for pressure is connected to the upper and lower electrodes are controlled by the control device) is 20 ~ 80MPa, the temperature increase rate is adjusted to 50 ~ 400 ℃ / min level. In the case of pressure, sintering may be insufficient when the pressure is 20 MPa or less, and 80 MPa may damage the carbon mold beyond the maximum strength of the currently commercially available carbon mold. Since the current applied from the DC power supply (controlled by the control device because the DC power supply is connected to the upper and lower electrodes) is different depending on the size of each equipment and the mold size, it is easy to control the temperature. If the temperature is lower than 50 ° C./min, the sintering time may be long. If the temperature is higher than 400 ° C./min, rapid sintering may occur, making it difficult to accurately predict sintering temperature.

After pressurization at the end of the sintering temperature and hold for several ten minutes, the furnace is cooled (furnace cooling) (S5). The retention time is preferably 5 to 10 minutes. The sintering end temperature refers to a temperature (temperature without change in height) in which the powder no longer contracts upon pressurization and temperature increase, which may vary depending on the type of powder, the size, shape and purity of the powder. Maintaining tens of minutes after the end of the sintering is a process in which the discharge plasma sintering takes place in a short time, whereas the material handled in the present invention is a precious metal having a very high sintering temperature, so that the sintered body is completely sintered to obtain a high density sintered body. . The grain growth may occur by increasing the sintering time, but since the holding time is several ten minutes, preferably 5-10 minutes, there is no large grain growth.

After the completion of the discharge plasma sintering process, it should be cooled in the furnace to 100 ℃ or lower while continuously reducing the pressure to protect the carbon mold. Since the coolant is connected to the upper and lower electrodes, fast cooling is possible by contacting the electrode with the mold while applying a minimum load. This method can be applied to metal materials with high thermal conductivity, but on the contrary, ceramic materials with low thermal conductivity should be refrained due to the risk of cracking due to different internal and external expansion due to rapid temperature gradient during cooling. .

Finally, the carbon sheet fixed to the sintered body is removed (S6).

Example 1

98 g of zinc oxide powder and 2 g of aluminum (Al) powder were weighed, mixed with a dispersant, mixed and pulverized using an attritor, and dried at 120 ° C. for at least 12 hours to sufficiently remove water in the powder. The moisture-depleted powder is heat treated at 650 ° C. for 2 hours to remove the dispersant. The prepared powder particle size had a distribution of 0.1 to 2 μm and the center particle size was 0.2 μm. After the carbon sheet was mounted on the discharge plasma sintering mold, and the powder from which the dispersant was removed was filled into a mold having an outer diameter of 200 mm and an inner diameter of 102 mm, the mold set was set inside the discharge plasma sintering apparatus chamber.

After setting, using a vacuum apparatus, the pressure was reduced to 1 Pa or less, pressurized to 40 MPa, and then a current was applied at 1000 A / min to adjust the temperature increase rate to 100 ° C / min. After the final sintering temperature was maintained for about 5 minutes at 1000 ℃, and the upper and lower electrodes were attached to the mold with a minimum load and cooled. After cooling below 100 ℃, release the vacuum, separate the sintered body to which the mold and the carbon sheet are fixed, remove the carbon sheet and adjust the thickness by grinding, and finally obtain a zinc oxide type sputtering target having a diameter of 4 inches and a thickness of 6 mm. Could.

Specific gravity, relative specific gravity, and total sintering time of the prepared targets are shown in Table 1.

Example 2

The powder prepared in Example 1 was set using the same mold, and then heated to the same conditions to find a temperature at which the height change was stabilized in order to find a condition in which sintering was completed, and then maintained at that temperature for 5 minutes. The temperature at which the height change was stabilized was 1200 ° C. A zinc oxide-based sputtering target having the same composition as in Example 1 having a diameter of 4 inches and a thickness of 6 mm was also prepared through the same cooling process and removal of carbon and polishing for thickness control.

Specific gravity, relative specific gravity, and the total sintering time of the prepared target are shown in Table 1.

Comparative Example 1

98 g of zinc oxide powder and 2 g of aluminum (Al) powder were weighed, and then a dispersant and a binder for molding were added, mixed and pulverized using ball milling, and dried at 120 ° C. for 12 hours.

The dried powder was uniformly filled into a mold having a diameter of 125 mm, and then first press-molded at a pressure of 1 ton, followed by cold hydrostatic molding at a pressure of 3 ton to improve molding density and remove directional residual stress in the molded body.

The prepared compacts were sintered at 1300 ° C., 1400 ° C., and 1500 ° C. for 10 hours, and then polished to prepare zinc oxide-based sputtering targets having a diameter of 4 inches and a thickness of 6 mm.

Specific gravity, relative specific gravity, and the total sintering time of the prepared target are shown in Table 1.

Comparative Example 2

In order to remove oxygen in the pores and to suppress volatilization of zinc oxide during sintering, the molded article manufactured under the same conditions as in Comparative Example 1 was sintered at 1300 ° C., 1400 ° C. and 1500 ° C. for 10 hours in an argon atmosphere of inert gas, and then polished. A zinc oxide-based sputtering target having a diameter of 4 inches and a thickness of 6 mm was prepared. Specific gravity, relative specific gravity, and total sintering time of the prepared targets are shown in Table 1.

At least one element of Al, Ti, Ga, B, Mg, Ni, Si, Sn, Ta, Ba, Y instead of adding aluminum powder to zinc oxide in Examples 1 and 2 and Comparative Examples 1 and 2 above The same result can be obtained even if it adds the compound containing.

Table 1

The target prepared as shown in Example 1 and Example 2 of Table 1 showed a high specific gravity in a short time. In particular, in Example 2 manufactured by the discharge plasma sintering method at 1200 ° C. at a temperature at which the height was stabilized, an ultra-high density target having a relative ratio of 99.8% of the relative ratio close to the theoretical ratio of the three-hour sintering furnace was manufactured.

On the other hand, the sputtering targets of Comparative Example 1 and Comparative Example 2 prepared in the air and in the argon atmosphere, respectively, according to the conventional method for producing a sintered body, the total sintering time is 10 times longer than that of Examples 1 and 2, and the relative specific gravity is also Appeared low. The relative density of 97.8% in the case of Comparative Example 2 prepared in the argon atmosphere was the highest density, but did not reach the relative weight of the sintered body produced by the discharge plasma sintering method.

In Comparative Example 1, the specific gravity decreases as the sintering temperature is increased because volatilization of zinc oxide occurs inside when sintering at a high temperature.

In Comparative Example 2, as the sintering temperature increases, the specific gravity increases, but the specific gravity does not increase above 97.8. The reason is that the closed pores are formed during the sintering and there is no channel for removing pores even when the sintering temperature increases. This is because pore removal is impossible.

Therefore, the method of manufacturing a zinc oxide-based sputtering target using the discharge plasma sintering method prevents the volatilization of zinc oxide during sintering at high temperatures, and close pores are not formed inside during sintering, thus having a high density close to theoretical density, and excellent physical properties. It can be seen that it provides a zinc oxide-based sputtering target having.

Herein, the present invention described above has been described with reference to the preferred embodiments, but those skilled in the art and those skilled in the art will variously modify the present invention without departing from the technical matters and scope of the present invention described in the claims below. And can be changed.

Since the discharge plasma sintering method can rapidly raise the temperature, the growth of the particles can be controlled, and a compact sintered body can be obtained in a short time, and the discharge plasma sintering process has the advantages of easy handling and low running cost.

In addition, even an sintered material can be easily sintered, and in particular, the sintering method so far has been difficult to sinter, for example, ceramic composite materials such as ZrO ₂ and Al ₂ O ₃ including polymer whiskers and fibers, Sintering of metal-based composite materials (MMC) and high temperature sintering have the advantage that they can be applied to amorphous materials that are susceptible to crystallization due to crystallization.

In the present invention, the zinc oxide-based powder is mixed, dried, and pulverized, and thus the manufacturing method is simple using the above-described discharge plasma sintering method, and the volatilization of zinc oxide is suppressed by the pressure applied during sintering and high density close to theoretical density is achieved. It provides a method for producing a zinc oxide-based sputtering target having excellent physical properties.

Claims (5)

In the manufacturing method of zinc oxide-based sputtering target using the discharge plasma sintering method, Grinding and drying the zinc oxide powder, Mounting a carbon sheet on a mold for discharging the plasma to fill the powder; Filling the mold having the carbon sheet mounted thereon with the powder subjected to the grinding and drying to prepare a mold set, and then setting the mold set in a discharge plasma sintering device chamber; A discharge plasma sintering step of depressurizing the chamber by an atmosphere control mechanism and then applying a pressure and heating the same by applying a current; Cooling the furnace in a furnace after pressurizing and maintaining 5 to 10 minutes in the elevated temperature near the final sintering temperature; A method for producing a zinc oxide-based sputtering target, comprising the step of removing a carbon sheet fixed to a cooled sintered body. The method of claim 1, The zinc oxide-based powder is zinc oxide-based sputtering, characterized in that a compound containing at least one element of Al, Ti, Ga, B, Mg, Ni, Si, Sn, Ta, Ba, Y is added to zinc oxide Target manufacturing method. The method of claim 1, The pressure applied in the discharge plasma sintering step is a zinc oxide-based sputtering target manufacturing method, characterized in that 20 ~ 80MPa. The method of claim 1, The discharge plasma sintering step is a zinc oxide-based sputtering target manufacturing method, characterized in that carried out in a vacuum atmosphere or inert gas atmosphere (Ar, N ₂ ). The method of claim 1, The discharge plasma sintering step of the zinc oxide-based sputtering target manufacturing method, characterized in that the temperature increase rate in the range of 50 ~ 400 ℃ / min.

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