Zinc oxide target and method for producing the same

Abstract

The application relates to the technical field of target material production, and discloses a preparation method of a zinc oxide target material, which comprises the following steps: mixing small-particle zinc oxide with a particle size of 1-3 microns and large-particle zinc oxide with a particle size of 3-5 microns according to a mass ratio of 1.5-4:1 to obtain mixed zinc oxide material; vacuum hot-pressing the mixed zinc oxide material to obtain a hot-pressed blank; and sintering the hot-pressed blank to obtain the zinc oxide target material. The zinc oxide target material prepared by the preparation method has a relatively high relative density, and during the preparation process, by adjusting various parameters, it is surprisingly found that when the parameters are a specific value, the improvement of the relative density is the most obvious.

Description

Technical Field

[0001] This invention relates to the field of target production technology, and in particular to a zinc oxide target and its preparation method. Background Technology

[0002] ZnO (Zinc Oxide) is a group II-VI direct bandgap semiconductor material with a wurtzite structure and a hexagonal prism crystal structure. ZnO resources are abundant, clean, and non-toxic. Due to its superior optoelectronic properties, it has found wide application in many fields such as gas sensors, solar cells, photodetectors, light-emitting diodes, surface acoustic wave devices, and laser systems. Currently, most research at home and abroad still focuses on ZnO thin films and their properties, with very little research on target materials. For the preparation of ZnO thin films, the performance of the corresponding target material greatly affects the performance of the resulting film; in other words, without high-performance target materials, there are no high-performance ZnO thin films. Therefore, research on the preparation process of target materials is equally important.

[0003] Chinese patent application 201180058840.8 discloses a zinc oxide sintered body, a sputtering target, and a zinc oxide film. The main components of the zinc oxide sintered body in this solution are zinc oxide and 30 to 1000 ppm of zirconium. At the same time, this solution also discloses a sputtering target formed from the above-mentioned zinc oxide sintered body.

[0004] The specification states that "there are no particular limitations on sintering conditions, but from the viewpoint of shortening the firing time and preventing cracking, the heating rate is preferably 10 to 400°C / hour. Furthermore, from the same viewpoint, the firing temperature is preferably 900°C to 1200°C. Moreover, from the viewpoint of obtaining a dense sintered body with a relative density of 97% or higher, the firing temperature is preferably 950°C to 1150°C. The cooling rate, from the viewpoint of preventing cracking, is preferably 10 to 400°C / hour. Especially to prevent cracking of the sintered body due to thermal shock, it is preferable to remove the sintered body from the furnace at a temperature close to room temperature." It also states that "the finer the particle size of the zinc oxide sintered body, the higher the strength. Therefore, the average particle size of the zinc oxide sintered body is preferably 1 to 15 μm, more preferably 1 to 10 μm."

[0005] Meanwhile, observation of the embodiments of this scheme reveals that the forming method used in the preparation process is pressure forming rather than hot pressing forming, and observation of the test data shows that the relative density of the sintered body obtained in each embodiment is between 97.6% and 98.5%.

[0006] Chinese patent application 201310412822.6 discloses a high-density zinc oxide-based target material and its preparation method. The method includes the following steps: a mixing step: adding a binder and water to the raw materials, mixing them evenly to obtain a uniform slurry, then drying and pulverizing the slurry to obtain dry powder particles with uniform particle size distribution; a binder removal and degassing step: loading the dry powder particles into a sleeve of corresponding size, and performing binder removal and degassing treatment; a hot isostatic pressing step: sealing the debonded and degassed sleeve and then performing hot isostatic pressing treatment; and an annealing step: annealing the ingot blank after removing the sleeve.

[0007] The zinc oxide-based target material prepared by this method has high density, with a relative density that can reach more than 99% of the theoretical density; uniform density, with almost the same density in all parts; large-scale target material size, up to 500mm×500mm×50mm; no pores or looseness, fine grains, with an average grain size of no more than 30μm;

[0008] However, it should be noted that although the scheme emphasizes limiting the average particle size of zinc oxide powder, specifying that the average particle size of zinc oxide is 0.005-5 micrometers, it can be seen from the embodiments of the scheme that the above-mentioned average particle size of 0.005-5 micrometers needs to be mixed with a binder and further processed into micrometer-sized particles by spray granulation before hot isostatic pressing. Furthermore, in the embodiments disclosed in the scheme, the particle size range of zinc oxide is between 20 nanometers and 1 micrometer. In actual production, using zinc oxide powder with a smaller particle size will undoubtedly increase the cost to a certain extent.

[0009] The problem this solution aims to solve is: how to further enrich the preparation methods of zinc oxide targets, and how to obtain zinc oxide targets with excellent relative density using these methods. Summary of the Invention

[0010] The purpose of this application is to provide a method for preparing zinc oxide target material, which prepares zinc oxide target material by producing micron-sized zinc oxide particles, and the prepared zinc oxide target material has good relative density.

[0011] Unless otherwise specified in this application: nM represents nanomoles per liter, μM represents micromoles per liter, mM represents millimoles per liter, and M represents moles per liter;

[0012] To achieve the above objectives, this application discloses a method for preparing a zinc oxide target, comprising the following steps:

[0013] Step 1: Mix small zinc oxide particles with a particle size of 1-3 micrometers and large zinc oxide particles with a particle size of 3-5 micrometers at a mass ratio of 1.5-4:1 to obtain the mixed zinc oxide material;

[0014] Step 2: Vacuum hot pressing of the mixed zinc oxide material to obtain a hot-pressed blank;

[0015] Step 3: Sinter the hot-pressed blank to obtain the zinc oxide target material.

[0016] More preferably, the particle size of the small zinc oxide particles is 2 to 3 micrometers, and the particle size of the large zinc oxide particles is 4 to 5 micrometers. Specifically, the particle size of the small zinc oxide particles includes, but is not limited to, 2 micrometers, 2.5 micrometers, and 3 micrometers, and the particle size of the large zinc oxide particles includes, but is not limited to, 4 micrometers, 4.5 micrometers, and 5 micrometers.

[0017] Preferably, step 2 specifically includes the following steps:

[0018] Step A1: Place the mixed zinc oxide material into a vacuum hot press furnace, and then evacuate the vacuum degree of the vacuum hot press furnace to 5 Pa;

[0019] Step A2: Turn on the heating and heat to 900-950℃ at a heating rate of 2-10℃ / min, then hold for 10-50 min, then pressurize to 45-70MPa, and hold for 60-100 min after pressurization.

[0020] Step A3: After the heat preservation and pressure holding are completed, the vacuum hot press furnace is cooled to room temperature at a cooling rate of 6-8℃ / min. After opening the furnace and demolding, the hot-pressed blank is obtained.

[0021] Preferably, step 3 specifically includes the following steps:

[0022] Step B1: Place the hot-pressed blank obtained in step A3 into an atmosphere sintering furnace for sintering. The sintering atmosphere is air. After heating is turned on, first raise the temperature to 1250-1300℃ at 1-3℃ / min, and then hold it for 24-48 hours.

[0023] Step B2: After the heat preservation is completed, the hot-pressed blank is cooled to room temperature with the furnace to obtain zinc oxide target material.

[0024] Preferably, the purity of the small-particle zinc oxide and the large-particle zinc oxide is greater than or equal to 3N.

[0025] It should be noted that the selection of zinc oxide raw material purity is not substantially related to the actual technical problem to be solved in this application, because the purity of the raw material directly affects and only affects the purity of the target material, and has no substantial impact on the relative density. However, it should be noted that in the actual production process, the price of zinc oxide will increase with the increase of zinc oxide purity. Therefore, it is recommended that operators select zinc oxide of different purities according to actual needs. The reason why this application selects zinc oxide with a purity of 3N and above is because this application has related needs in actual production.

[0026] Preferably, the mass ratio of small zinc oxide particles to large zinc oxide particles is 3 to 4:1;

[0027] Step A2 is as follows: heat to 900-950℃ at a heating rate of 6-10℃ / min, then hold at that temperature for 10-50min, then pressurize to 45-60MPa, and hold at that temperature and pressure for 60-100min.

[0028] Preferably, the mass ratio of small zinc oxide particles to large zinc oxide particles is 1.5 to 3:1;

[0029] Step A2 is as follows: heat to 900-950℃ at a heating rate of 2-6℃ / min, then hold for 10-50min, then pressurize to 60-70MPa, and hold for 60-100min after pressurization.

[0030] In addition, this application also discloses a zinc oxide target material, which is prepared by the above-described method for preparing zinc oxide targets.

[0031] Preferably, the relative density of the zinc oxide target is 99.0% to 99.9%.

[0032] The beneficial effects of this application are as follows: The zinc oxide target preparation method disclosed in this application, through the combination of small and large zinc oxide particles, enables the preparation of a target with good relative density without the need for nanoscale raw materials. We speculate that the reason for this phenomenon may be that, during the vacuum hot pressing process of zinc oxide particles, large zinc oxide particles form the basic framework of the zinc oxide target, while small zinc oxide particles fill the gaps between the large zinc oxide particles. This phenomenon improves the compactness of the stacking between zinc oxide particles, thereby increasing the relative density. Furthermore, in actual implementation, we have further optimized the production process, further improving the relative density of the target without increasing costs. Detailed Implementation

[0033] In the description of this invention, it should be noted that unless specific conditions are specified in the examples, conventional conditions or conditions recommended by the manufacturer shall apply. Reagents or instruments whose manufacturers are not specified are all commercially available products.

[0034] The present invention will now be clearly and completely described in conjunction with embodiments thereof. Obviously, the described embodiments are merely some, not all, of the embodiments of the present invention. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0035] Example 1

[0036] Step 1: Mix small zinc oxide particles with a purity of 3N and a particle size of 1 micrometer with large zinc oxide particles with a particle size of 5 micrometers at a mass ratio of 1.5:1 to obtain the mixed zinc oxide material;

[0037] Step A1: Place the mixed zinc oxide material into a vacuum hot press furnace, and then evacuate the vacuum degree of the vacuum hot press furnace to 5 Pa;

[0038] Step A2: Turn on the heating and heat to 950°C at a rate of 10°C / min. Then hold the temperature for 50 min, then pressurize to 70 MPa and hold the temperature and pressure for 100 min.

[0039] Step A3: After the heat preservation and pressure holding are completed, the vacuum hot press furnace is cooled to room temperature at a cooling rate of 6℃ / min. After opening the furnace and demolding, the hot-pressed blank is obtained.

[0040] Step B1: Place the hot-pressed blank obtained in step A3 into an atmosphere sintering furnace for sintering. The sintering atmosphere is air. After turning on the heating, first raise the temperature to 1250℃ at 3℃ / min, and then hold it at that temperature for 24 hours.

[0041] Step B2: After the heat preservation is completed, the hot-pressed blank is cooled to room temperature with the furnace to obtain zinc oxide target material.

[0042] Example 2

[0043] Step 1: Mix zinc oxide particles with a purity of 3.5N and a particle size of 2 micrometers and zinc oxide particles with a particle size of 3 micrometers at a mass ratio of 4:1 to obtain the mixed zinc oxide material;

[0044] Step A1: Place the mixed zinc oxide material into a vacuum hot press furnace, and then evacuate the vacuum degree of the vacuum hot press furnace to 5 Pa;

[0045] Step A2: Turn on the heating and heat to 900℃ at a rate of 2℃ / min, then hold for 10 min, then pressurize to 45MPa, and hold for 60 min after pressurization.

[0046] Step A3: After the heat preservation and pressure holding are completed, the vacuum hot press furnace is cooled to room temperature at a cooling rate of 7℃ / min. After opening the furnace and demolding, the hot-pressed blank is obtained.

[0047] Step B1: Place the hot-pressed blank obtained in step A3 into an atmosphere sintering furnace for sintering. The sintering atmosphere is air. After heating is turned on, the temperature is first increased to 1300℃ at 1℃ / min, and then held for 48 hours.

[0048] Step B2: After the heat preservation is completed, the hot-pressed blank is cooled to room temperature with the furnace to obtain zinc oxide target material.

[0049] Example 3

[0050] Step 1: Mix zinc oxide particles with a purity of 3N and a particle size of 3 micrometers with zinc oxide particles with a particle size of 4 micrometers at a mass ratio of 3:1 to obtain the mixed zinc oxide material;

[0051] Step A1: Place the mixed zinc oxide material into a vacuum hot press furnace, and then evacuate the vacuum degree of the vacuum hot press furnace to 5 Pa;

[0052] Step A2: Turn on the heating and heat to 900℃ at a rate of 2℃ / min, then hold for 30min, then pressurize to 60MPa, and hold for 80min after pressurization.

[0053] Step A3: After the heat preservation and pressure holding are completed, the vacuum hot press furnace is cooled to room temperature at a cooling rate of 8℃ / min. After opening the furnace and demolding, the hot-pressed blank is obtained.

[0054] Step B1: Place the hot-pressed blank obtained in step A3 into an atmosphere sintering furnace for sintering. The sintering atmosphere is air. After heating is turned on, the temperature is first increased to 1275℃ at 2℃ / min, and then held for 36 hours.

[0055] Step B2: After the heat preservation is completed, the hot-pressed blank is cooled to room temperature with the furnace to obtain zinc oxide target material.

[0056] Example 4

[0057] Step 1: Mix zinc oxide particles with a purity of 3N and a particle size of 2.5 micrometers and zinc oxide particles with a particle size of 4.5 micrometers at a mass ratio of 3.5:1 to obtain the mixed zinc oxide material;

[0058] Step A1: Place the mixed zinc oxide material into a vacuum hot press furnace, and then evacuate the vacuum degree of the vacuum hot press furnace to 5 Pa;

[0059] Step A2: Turn on the heating and heat to 900℃ at a rate of 8℃ / min, then hold for 30min, then pressurize to 50MPa, and hold for 70min after pressurization.

[0060] Step A3: After the heat preservation and pressure holding are completed, the vacuum hot press furnace is cooled to room temperature at a cooling rate of 7℃ / min. After opening the furnace and demolding, the hot-pressed blank is obtained.

[0061] Step B1: Place the hot-pressed blank obtained in step A3 into an atmosphere sintering furnace for sintering. The sintering atmosphere is air. After turning on the heating, first raise the temperature to 1250℃ at 3℃ / min, and then hold it at that temperature for 24 hours.

[0062] Step B2: After the heat preservation is completed, the hot-pressed blank is cooled to room temperature with the furnace to obtain zinc oxide target material.

[0063] Example 5

[0064] Step 1: Mix zinc oxide particles with a purity of 3N and a particle size of 2.5 micrometers and zinc oxide particles with a particle size of 4.5 micrometers at a mass ratio of 2.5:1 to obtain the mixed zinc oxide material;

[0065] Step A1: Place the mixed zinc oxide material into a vacuum hot press furnace, and then evacuate the vacuum degree of the vacuum hot press furnace to 5 Pa;

[0066] Step A2: Turn on the heating and heat to 950°C at a rate of 3°C / min. Then hold the temperature for 30 minutes, then pressurize to 65MPa and hold the temperature and pressure for 70 minutes.

[0067] Step A3: After the heat preservation and pressure holding are completed, the vacuum hot press furnace is cooled to room temperature at a cooling rate of 7℃ / min. After opening the furnace and demolding, the hot-pressed blank is obtained.

[0068] Step B1: Place the hot-pressed blank obtained in step A3 into an atmosphere sintering furnace for sintering. The sintering atmosphere is air. After heating is turned on, the temperature is first increased to 1300℃ at 1.5℃ / min, and then held for 42 hours.

[0069] Step B2: After the heat preservation is completed, the hot-pressed blank is cooled to room temperature with the furnace to obtain zinc oxide target material.

[0070] Comparative Example 1

[0071] The process is basically the same as in Example 1, except that in step 1, the particle size of the small zinc oxide particles is 1 micrometer and the particle size of the large zinc oxide particles is 10 micrometers.

[0072] Comparative Example 2

[0073] The process is basically the same as in Example 1, except that in step 1, the particle size of the small zinc oxide particles is 20 nanometers and the particle size of the large zinc oxide particles is 5 micrometers.

[0074] Comparative Example 3

[0075] The process is basically the same as in Example 1, except that in step 1, large zinc oxide particles with a particle size of 5 micrometers are used instead of small zinc oxide particles.

[0076] Comparative Example 4

[0077] It is basically the same as Example 1, except that in step A2, the heating rate is 20°C / min.

[0078] Comparative Example 5

[0079] It is basically the same as Example 1, except that in step A2, the heat preservation time is 5 minutes.

[0080] Comparative Example 6

[0081] It is basically the same as Example 1, except that in step A2, the pressure is increased to 20MPa after heat preservation.

[0082] Comparative Example 7

[0083] It is basically the same as Example 1, except that in step A2, the heat preservation and pressure holding time is 30 minutes.

[0084] Performance testing:

[0085] Target relative density test:

[0086] The relative density of the target material was tested using the Archimedes displacement method, and the test results are shown in Table 1.

[0087] Table 1: Relative Density Test Table for Target Materials

[0088]

[0089]

[0090] Results analysis:

[0091] As can be seen from Examples 1-3, when the zinc oxide is a mixture of 3-micron small zinc oxide particles and 4-micron large zinc oxide particles in a 3:1 mass ratio, a zinc oxide target with excellent relative density can be obtained by combining it with a lower heating rate. Compared with Examples 1 and 2, this zinc oxide target has a significant advantage in relative density. We believe that the reason for this phenomenon is that, on the one hand, the proportion of small zinc oxide particles is higher than that of Example 1. Although the small zinc oxide particles in Example 3 have a larger particle size than those in Example 1, the increased proportion improves their ability to fill the gaps between the large zinc oxide particles. In addition, the further control of the heating rate makes Example 3 reach the peak temperature later than Example 1, prolonging the heating time of Example 3. Therefore, the mixing and stacking of zinc oxide particles of different sizes are further improved, so that it still shows an increase in relative density under lower pressure.

[0092] On the other hand, compared with Example 2, although the large and small zinc oxide particles in Example 3 have larger particle sizes and a lower proportion of small zinc oxide particles, the relative density of Example 3 is more advantageous because the pressure during the pressurization process is higher than that in Example 2. From the above two aspects, we can deduce three conclusions:

[0093] 1. As the proportion of small-particle zinc oxide increases, the relative density of the target material is improved to a certain extent, but this effect has an upper limit, and the improvement becomes less significant after reaching a certain level.

[0094] 2. As the overall particle size of both large and small zinc oxide particles decreases, the relative density of the target material is improved to a certain extent. However, when the zinc oxide particles in Examples 1-3 are all in the micron range, the improvement effect has an upper limit, and it becomes less significant after reaching a certain level.

[0095] 3. Changes in pressure and heating rate can increase the relative density of the target material to some extent. It is certain that the effect of pressure on the target material has an upper limit, and the effect becomes less significant after reaching a certain level. As for the effect of heating rate, i.e., the time to reach peak temperature, on the relative density of the target material, it is currently uncertain whether there is an upper limit. However, it should be noted that as the heating rate decreases, the production cost increases continuously. Therefore, in actual production, while increasing the relative density of the target material, it is more suitable for large-scale production to maximize the heating rate.

[0096] II. As can be seen from Examples 1 and 4-5, Example 4 further increased the proportion of small-particle zinc oxide compared to Example 1. It also used both larger-particle zinc oxide and even smaller-particle zinc oxide, and increased the relative density of the target material to 99.8% at a heating rate of 8°C / min and a pressure of 50 MPa. We speculate that this phenomenon is the result of further optimization of various parameters during the production process. In actual production, we attempted to further reduce the overall particle size of the zinc oxide, increase the pressure, or decrease the heating rate individually; however, the results were comparable to those of Example 4. Therefore, we believe that, under the premise of ensuring production costs, the relevant parameters used in Example 4 are more acceptable to us.

[0097] Of course, the effects of Example 5 and Example 4 are comparable, but the difference is that the heating time and pressure during hot pressing in Example 5 are longer. However, the proportion of small zinc oxide particles in Example 5 is smaller. Given that the effects of Example 4 and Example 5 are comparable, the specific choice can be determined based on the actual situation.

[0098] III. As can be seen from Example 1 and Comparative Example 1, when the particle size of the large zinc oxide particles increases to 10 micrometers, the relative density of the target material decreases significantly. We believe that the reason for this phenomenon is that the gaps between the large zinc oxide particles are too large, and when the particle size of the large zinc oxide particles is too large, defects will be generated inside the target material.

[0099] IV. As can be seen from Example 1 and Comparative Example 2, even if the particle size of zinc oxide is further reduced to the nanoscale, the improvement in the relative density of the target material is still not significant. This also proves that reducing the particle size of zinc oxide has a limited effect on improving the target material. Furthermore, as the particle size of zinc oxide decreases, the cost of zinc oxide raw materials gradually increases. Therefore, we do not believe that the scheme of Comparative Example 2 is suitable for actual production needs.

[0100] V. As can be seen from Example 1 and Comparative Examples 3-7, when zinc oxide particles with a particle size of 5 micrometers are used to prepare the target material, the relative density of the target material is reduced to a certain extent. Based on the above conclusions, we believe that the reason for this phenomenon is that the gaps between the large zinc oxide particles are not filled, which leads to a decrease in relative density.

[0101] When the heating rate is too fast, the holding time is too short, the pressure during the hot pressing process is too low, and the holding and pressure holding time is too short, we speculate that the decrease in the relative density of the target material is due to the fact that the gaps inside the target material are not effectively filled.

[0102] The above embodiments are preferred embodiments of the present invention, but the embodiments of the present invention are not limited to the above embodiments. Any changes, modifications, substitutions, combinations, or simplifications made without departing from the spirit and principle of the present invention shall be considered equivalent substitutions and shall be included within the protection scope of the present invention.

Claims

1. A method for preparing a zinc oxide target, characterized in that, Includes the following steps: Step 1: Mix small zinc oxide particles with a particle size of 1-3 micrometers with large zinc oxide particles with a particle size of 3-5 micrometers (excluding 3 micrometers) at a mass ratio of 1.5-4:1 to obtain the mixed zinc oxide material; Step 2 specifically includes the following steps: Step A1: Place the mixed zinc oxide material into a vacuum hot press furnace, and then evacuate the vacuum degree of the vacuum hot press furnace to 5 Pa; Step A2: Turn on the heating and heat to 900-950℃ at a heating rate of 2-10℃ / min, then hold for 10-50 min, then pressurize to 45-70MPa, and hold for 60-100 min after pressurization. Step A3: After the heat preservation and pressure holding are completed, the vacuum hot press furnace is cooled to room temperature at a cooling rate of 6-8℃ / min. After opening the furnace and demolding, the hot-pressed blank is obtained. When the mass ratio of small zinc oxide particles to large zinc oxide particles is 3 to 4:1 (excluding 3:1); Step A2 is as follows: heat to 900-950℃ at a heating rate of 6-10℃ / min, then hold at that temperature for 10-50min, then pressurize to 45-60MPa, and hold at that temperature and pressure for 60-100min. When the mass ratio of small zinc oxide particles to large zinc oxide particles is 1.5 to 3:1; Step A2 is as follows: heat to 900-950℃ at a heating rate of 2-6℃ / min, then hold at that temperature for 10-50min, then pressurize to 60-70MPa, and hold at that temperature and pressure for 60-100min. Step 3 specifically includes the following steps: Step B1: Place the hot-pressed blank obtained in step A3 into an atmosphere sintering furnace for sintering. The sintering atmosphere is air. After heating is turned on, first raise the temperature to 1250-1300℃ at 1-3℃ / min, and then hold it for 24-48 hours. Step B2: After the heat preservation is completed, the hot-pressed blank is cooled to room temperature with the furnace to obtain zinc oxide target material.

2. The method for preparing the zinc oxide target according to claim 1, characterized in that, The purity of the small-particle zinc oxide and the large-particle zinc oxide is greater than or equal to 3N.

3. A zinc oxide target material, characterized in that, The zinc oxide target was prepared using the method described in any one of claims 1-2.

4. The zinc oxide target material according to claim 3, characterized in that, The relative density of the zinc oxide target is 99.0-99.9%.

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