Method for the production of high uniformity oxide targets for reactive plasma deposition

Abstract

The application relates to the technical field of semiconductor material preparation, and provides a preparation method of a high-uniformity oxide target material for reactive plasma deposition, which adopts a cellulose pore-forming agent, and through a segmented degreasing process, PVA binders and the cellulose pore-forming agent are sequentially decomposed in different temperature intervals, gas slowly and orderly escapes, the problems of internal pores and cracks of the target material caused by the simultaneous escape of a large amount of gas in the traditional process are avoided, and the product yield is increased from about 70% in the traditional process to more than 95%. Through optimization of a spray granulation process, a granulation powder with high sphericity and good fluidity is prepared, and a cold isostatic pressing forming process is used, so that the green density of the target material is increased from 55-60% of the theoretical density in the traditional process to more than 65%, thereby laying a good foundation for subsequent sintering densification.

Description

Technical Field

[0001] This invention relates to the field of semiconductor material preparation technology, and in particular to a method for preparing a highly uniform oxide target for reactive plasma deposition. Background Technology

[0002] Reactive plasma deposition (RPD) is a highly efficient thin film fabrication process widely used in the preparation of transparent conductive oxide (TCO) thin films for display panels, solar cells, and semiconductor devices. Compared with traditional magnetron sputtering, RPD offers significant advantages such as high deposition rate, good film crystallinity, and low damage.

[0003] As the core consumable material in the RPD process, the density, strength, pore structure, and uniformity of the target material directly determine the quality and production efficiency of the deposited film. Currently, oxide targets for RPD are typically prepared using powder metallurgy processes, which mainly include powder mixing, forming, debinding, and sintering.

[0004] Existing technologies commonly use polyvinyl alcohol (PVA) as a binder, along with lipids such as stearic acid and paraffin wax as dispersants and pore-forming agents. However, this technical solution has the following key drawbacks: The degreasing process is difficult to control: the decomposition temperature ranges of PVA and lipid additives highly overlap (usually in the range of 200-400℃), causing a large amount of gas to escape rapidly during the degreasing process, which can easily form pores, cracks or even breakage inside the target material, seriously affecting the product yield.

[0005] Uneven pore-forming effect: Lipid-based pore-forming agents have poor dispersibility in powder and are prone to agglomeration, resulting in uneven pore size and distribution inside the target material, making it impossible to form a continuous and stable skeleton structure.

[0006] Poor density uniformity: The uneven pressure distribution in the traditional dry pressing process leads to significant gradient differences in the density of the target green body. After sintering, the overall density uniformity of the target body is poor, usually only within ±2%.

[0007] Insufficient target strength: The uneven pore structure and low skeleton density result in low mechanical strength of the target, making it prone to breakage during transportation, installation and sputtering.

[0008] Uneven sputtering consumption: Inhomogeneity in density and pore structure leads to large differences in the consumption rate of the target material during RPD sputtering, which not only reduces the utilization rate of the target material, but also causes inhomogeneity in the thickness and electrical properties of the deposited film, affecting the quality of the final product.

[0009] Therefore, developing a method for preparing oxide targets for RPD that can achieve ordered degreasing, uniform pore formation, and improve the density uniformity and mechanical strength of the target material has become a technical problem that urgently needs to be solved in this field. Summary of the Invention

[0010] In view of this, the purpose of this invention is to provide a method for preparing a highly uniform oxide target for reactive plasma deposition, thereby solving the problems in the prior art.

[0011] To achieve the above objectives, the present invention provides a method for preparing a highly uniform oxide target for reactive plasma deposition, comprising the following steps: Step 1, Powder pretreatment: The oxide raw material powder is first ball-milled, then dried at 80-120℃ for 12-24 hours to remove moisture; and then calcined at 1400-1580℃ for 4-24 hours in an oxygen atmosphere to achieve grain fusion and phase formation. After cooling, it is ball-milled again to disperse the powder. Step 2, mixing and granulation: The pretreated oxide powder, 0.5-3.0 wt% of cellulose pore-forming agent, 0.1-1.0 wt% of PVA binder, and deionized water are added to a high-speed mixer and mixed at 1000-3000 rpm for 5-15 minutes to form a uniform slurry; then, spherical particles are prepared by spray granulation. Step 3, cold isostatic pressing: The powder obtained by spray granulation is loaded into the mold, pre-pressed at 10-50MPa pressure, and then cold isostatic pressing is performed at 150-300MPa pressure for 5-30 minutes to obtain a high-density target green body with no density gradient. Step 4, Degreasing: Place the target blank in a degreasing furnace and perform segmented degreasing in an air / oxygen atmosphere; Step 5, sintering densification: The degreased target material is placed in a sintering furnace and heated to 1400-1600℃ at a rate of 2-5℃ / min under an oxygen atmosphere, held for 8-24 hours, and then cooled to room temperature with the furnace to obtain an oxide target material with a relative density of 60±1%.

[0012] Preferably, the oxide raw material powder is any one of indium tin oxide (ITO), indium cerium oxide (ICO), indium zinc oxide (IZO), indium gallium oxide (IGO), or indium tungsten oxide (IWO).

[0013] Preferably, the proportion of indium oxide in the oxide raw material powder is 80-99 wt%.

[0014] Preferably, the cellulose-based pore-forming agent is any one or more combinations of methylcellulose (MC), hydroxypropyl methylcellulose (HPMC), carboxymethyl cellulose (CMC), or microcrystalline cellulose.

[0015] Preferably, the fourth step of degreasing includes: In the first stage, the temperature is increased to 200-260℃ at a rate of 0.5-1.0℃ / min and held for 2-4 hours to completely remove moisture and low-boiling-point impurities. In the second stage, the temperature is increased to 300-350℃ at a rate of 0.2-0.5℃ / min and held for 4-8 hours to allow the PVA adhesive to completely decompose and slowly escape. In the third stage, the temperature is increased to 450-550℃ at a rate of 0.3-0.8℃ / min and held for 3-6 hours to allow the cellulose pore-forming agent to decompose uniformly and form the initial pore structure.

[0016] Preferably, in step one, the powder is first ball-milled until the particle size D50 is 0.5-2.0 μm and D90 ≤ 5.0 μm; then it is ball-milled again until the particle size D50 is 0.5-2.0 μm and D90 ≤ 5.0 μm.

[0017] Preferably, the particles obtained in step two have a particle size of 50-150 μm and a loose packing density of 1.2-1.8 g / cm³.

[0018] The beneficial effects of this invention are: Achieving orderly degreasing significantly reduces sintering cracking. This invention employs a cellulose-based pore-forming agent, whose decomposition temperature (400-550℃) forms a significant temperature gradient with that of the PVA binder (250-350℃). Through a segmented degreasing process, the PVA binder and the cellulose-based pore-forming agent decompose sequentially within different temperature ranges, allowing gases to escape slowly and systematically. This avoids the problems of internal porosity and cracks in the target material caused by the simultaneous escape of large amounts of gas in traditional processes, increasing the product yield from approximately 70% to over 95%.

[0019] Significantly improves powder flowability and green body density This invention optimizes the spray granulation process to prepare granulated powder with high sphericity and good flowability (flowability ≤30s / 50g). Combined with cold isostatic pressing, the density of the target green body is increased from the traditional theoretical density of 55-60% to more than 65%, laying a good foundation for subsequent sintering densification.

[0020] Forming a uniform mesh-like pore structure and a high-density skeleton Cellulose-based pore-forming agents have good dispersibility in powder. After decomposition, they form a uniform and continuously distributed mesh-like pore structure inside the target material, while retaining a higher density ceramic skeleton. This significantly enhances the mechanical properties and impact resistance of the target material, resulting in a substantial reduction in the cracking rate of the target material during use.

[0021] Significantly improve the uniformity of target material density Cold isostatic pressing (CIP) provides isotropic and uniform pressure, eliminating the density gradient problem inherent in traditional dry pressing. The overall density uniformity of the target material prepared by this invention can reach within ±0.5%, far superior to the ±2% level of traditional processes, perfectly matching the stringent density requirements of the RPD process.

[0022] Improve sputtering performance and enhance product uniformity The uniform density and mesh-like pore structure make the target material consumed more evenly during RPD sputtering, improving the thickness uniformity of the deposited film from ±5% to within ±2%, significantly reducing the fluctuation range of electrical properties, and showing a decreasing trend in film resistivity and an increasing trend in mobility, thus improving the quality and consistency of the final product. Detailed Implementation

[0023] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to specific embodiments.

[0024] It should be noted that, unless otherwise defined, the technical or scientific terms used in this invention should have the ordinary meaning understood by one of ordinary skill in the art to which this invention pertains. The terms "first," "second," and similar terms used in this invention do not indicate any order, quantity, or importance, but are merely used to distinguish different components. Terms such as "comprising" or "including" mean that the element or object preceding the word encompasses the elements or objects listed following the word and their equivalents, without excluding other elements or objects. Terms such as "connected" or "linked" are not limited to physical or mechanical connections, but can include electrical connections, whether direct or indirect. Terms such as "upper," "lower," "left," and "right" are used only to indicate relative positional relationships; when the absolute position of the described object changes, the relative positional relationship may also change accordingly.

[0025] Example 1: Preparation of porous ITO sputtering target with 90 wt% indium oxide content Powder pretreatment: In2O3 powder and SnO2 powder were mixed at a mass ratio of 90:10 (indium oxide accounted for 90wt%) and subjected to planetary ball milling to control the powder particle size D50=1.0μm and D90=4.2μm; dried at 100℃ for 18 hours; then calcined at 1500℃ for 12 hours in an oxygen atmosphere, cooled, and then ball-milled again to disperse to D50=1.2μm.

[0026] Mixing and granulation: The pretreated ITO powder, 1.2 wt% hydroxypropyl methylcellulose (HPMC), 0.4 wt% PVA binder and deionized water are added to a high-speed mixer and mixed at 2000 rpm for 10 minutes to prepare a uniform slurry with a solid content of 62%; spherical particles are prepared by spray granulation, with the inlet air temperature controlled at 220℃ and the outlet air temperature at 110℃, to obtain granulated powder with a particle size of 60-120μm and a loose packing density of 1.5g / cm³.

[0027] Cold isostatic pressing: The granulated powder is loaded into a rubber mold, pre-pressed at 30MPa for 5 minutes, and then cold isostatically pressed at 220MPa for 15 minutes to obtain an ITO target green with a green density of 58% of the theoretical density.

[0028] Orderly degreasing: Place the green body in a degreasing furnace and, under air atmosphere: heat to 230℃ at 0.7℃ / min and hold for 3 hours; heat to 320℃ at 0.3℃ / min and hold for 6 hours; heat to 500℃ at 0.5℃ / min and hold for 4 hours.

[0029] Sintering densification: The degreased target material is placed in an oxygen atmosphere sintering furnace, heated to 1520℃ at 3℃ / min and held for 12 hours, and then cooled with the furnace to obtain the finished ITO porous target material.

[0030] Example 2: Preparation of porous sputtering target with 90 wt% indium oxide (IZO) content Powder pretreatment: In2O3 powder and ZnO powder were mixed at a mass ratio of 90:10 (indium oxide accounted for 90wt%), and ball-milled to D50=0.8μm and D90=3.8μm; dried at 90℃ for 20 hours; then calcined at 1450℃ for 18 hours in an oxygen atmosphere, cooled, and ball-milled again to D50=1.0μm.

[0031] Mixing and granulation: The pretreated IZO powder, 1.8 wt% carboxymethyl cellulose (CMC), 0.6 wt% PVA binder and deionized water are added to a high-speed mixer and mixed at 2500 rpm for 8 minutes to prepare a uniform slurry with a solid content of 60%; spray granulation is then performed to obtain granulated powder with a particle size of 50-100 μm and a loose packing density of 1.4 g / cm³.

[0032] Cold isostatic pressing: First, pre-press at 25MPa for 8 minutes, then hold at 250MPa for 20 minutes to obtain an IZO target green with a green density of 57% of the theoretical density.

[0033] Orderly degreasing: Heat to 220℃ at 0.6℃ / min and hold for 3.5 hours; heat to 330℃ at 0.4℃ / min and hold for 5 hours; heat to 480℃ at 0.6℃ / min and hold for 5 hours.

[0034] Sintering densification: The temperature was increased to 1480℃ at 2.5℃ / min and held for 16 hours, followed by furnace cooling to obtain the finished IZO porous sputtering target.

[0035] Example 3: Preparation of ICO porous target material with 95 wt% indium oxide content Powder pretreatment: In2O3 powder and CeO2 powder were mixed at a mass ratio of 95:5 (indium oxide accounted for 95wt%), and ball-milled to D50=1.5μm and D90=4.8μm; dried at 110℃ for 15 hours; then calcined at 1550℃ for 8 hours in an oxygen atmosphere, cooled, and ball-milled again to D50=1.6μm.

[0036] Mixing and granulation: The pretreated ICO powder is added to a high-speed mixer with 0.8 wt% methylcellulose (MC), 0.3 wt% PVA binder and deionized water, and mixed at 1800 rpm for 12 minutes to prepare a uniform slurry with a solid content of 65%; spray granulation is then performed to obtain granulated powder with a particle size of 70-130 μm and a loose packing density of 1.6 g / cm³.

[0037] Cold isostatic pressing: First, pre-press at 35MPa for 3 minutes, then hold at 200MPa for 10 minutes to obtain an ICO target green with a green density of 59% of the theoretical density.

[0038] Orderly degreasing: Heat to 240℃ at 0.8℃ / min and hold for 2.5 hours; heat to 310℃ at 0.25℃ / min and hold for 7 hours; heat to 520℃ at 0.4℃ / min and hold for 3.5 hours.

[0039] Sintering densification: The temperature is increased to 1550℃ at 3.5℃ / min and held for 10 hours, then cooled in the furnace to obtain the finished ICO porous target material.

[0040] Example 4: Preparation of porous sputtering target with 85 wt% indium oxide (IWO) content Powder pretreatment: In2O3 powder and WO3 powder were mixed at a mass ratio of 85:15 (indium oxide accounted for 85wt%), and ball-milled to D50=1.2μm and D90=4.5μm; dried at 105℃ for 16 hours; then calcined at 1520℃ for 10 hours in an oxygen atmosphere, cooled, and ball-milled again to D50=1.3μm.

[0041] Mixing and granulation: The pretreated IWO powder, 2.2 wt% microcrystalline cellulose, 0.5 wt% PVA binder and deionized water are added to a high-speed mixer and mixed at 2200 rpm for 9 minutes to prepare a uniform slurry with a solid content of 63%; spray granulation is then carried out to obtain granulated powder with a particle size of 65-125 μm and a loose packing density of 1.45 g / cm³.

[0042] Cold isostatic pressing: First, pre-press at 28MPa for 6 minutes, then hold at 230MPa for 18 minutes to obtain an IWO target green with a green density of 57.5% of the theoretical density.

[0043] Orderly degreasing: Heat to 225℃ at 0.65℃ / min and hold for 3 hours; heat to 325℃ at 0.35℃ / min and hold for 5.5 hours; heat to 490℃ at 0.55℃ / min and hold for 4.5 hours.

[0044] Sintering densification: The temperature was increased to 1500℃ at 2.8℃ / min and held for 14 hours, followed by furnace cooling to obtain the finished IGO porous target material.

[0045] Comparative Example 1: Preparation of porous ITO sputtering target with 90 wt% indium oxide content using conventional process The difference from Example 1 is as follows: No pre-calcination treatment of the raw material powder is performed; Instead of using cellulose-based pore-forming agents, 2.0 wt% paraffin is used as the pore-forming agent. Cold isostatic pressing is not performed; instead, unidirectional dry pressing at 30 MPa is used. The degreasing process uses a single heating rate: heating to 500℃ at 1℃ / min and holding for 10 hours.

[0046] Comparative Example 2: Preparation of porous ITO sputtering material with 90 wt% indium oxide content without cold isostatic pressing process The difference from Example 1 is as follows: Cold isostatic pressing is not performed; instead, unidirectional dry pressing at 30 MPa is used. The remaining process parameters are exactly the same as in Example 1.

[0047] Comparative Example 3: Preparation of 90wt% Indium Oxide (ITO) Porous Target Material using a Cellulose-Free Pore-Forming Agent Process The difference from Example 1 is as follows: Instead of using cellulose-based pore-forming agents, 2.0 wt% paraffin is used as the pore-forming agent. The degreasing process uses a single heating rate: heating to 500℃ at 1℃ / min and holding for 10 hours; The remaining process parameters are exactly the same as in Example 1.

[0048] Performance Testing and Comparison The targets prepared in the above embodiments and comparative examples were subjected to performance tests. The test items included: green density, final relative density, density uniformity, flexural strength, sintering cracking rate, target utilization rate, and uniformity of deposited film thickness. The test results are shown in the table below: Test instructions: Density uniformity: The density of the target material at nine points, including the center and edge, was tested using the Archimedes method, and the deviation between the maximum and minimum values ​​was calculated. Sintering cracking rate: The percentage of macroscopic cracks found in 100 samples; Target utilization rate: The proportion of mass loss to the initial mass when RPD sputtering results in significant uneven erosion of the target. Thin film thickness uniformity: A 100 nm thick thin film was deposited on a 300 mm × 300 mm glass substrate, and the thickness deviation at 25 points was tested.

[0049] Those skilled in the art should understand that the discussion of any of the above embodiments is merely exemplary and is not intended to imply that the scope of the invention is limited to these examples; within the framework of the invention, the technical features of the above embodiments or different embodiments can also be combined, the steps can be implemented in any order, and many other variations of different aspects of the invention as described above exist, which are not provided in detail for the sake of brevity. Any omissions, modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the invention should be included within the scope of protection of the invention.

Claims

1. A method for preparing a highly uniform oxide target for reactive plasma deposition, characterized in that, Includes the following steps: Step 1, Powder pretreatment: The oxide raw material powder is first ball-milled, then dried at 80-120℃ for 12-24 hours to remove moisture; and then calcined at 1400-1580℃ for 4-24 hours in an oxygen atmosphere to achieve grain fusion and phase formation. After cooling, it is ball-milled again to disperse the powder. Step 2, mixing and granulation: The pretreated oxide powder, 0.5-3.0 wt% of cellulose pore-forming agent, 0.1-1.0 wt% of PVA binder, and deionized water are added to a high-speed mixer and mixed at 1000-3000 rpm for 5-15 minutes to form a uniform slurry; then, spherical particles are prepared by spray granulation. Step 3, cold isostatic pressing: The powder obtained by spray granulation is loaded into the mold, pre-pressed at 10-50MPa pressure, and then cold isostatic pressing is performed at 150-300MPa pressure for 5-30 minutes to obtain a high-density target green body with no density gradient. Step 4, Degreasing: Place the target blank in a degreasing furnace and perform segmented degreasing in an air / oxygen atmosphere; Step 5, sintering densification: The degreased target material is placed in a sintering furnace and heated to 1400-1600℃ at a rate of 2-5℃ / min under an oxygen atmosphere, held for 8-24 hours, and then cooled to room temperature with the furnace to obtain an oxide target material with a relative density of 60±1%.

2. The method for preparing a highly uniform oxide target for reactive plasma deposition according to claim 1, characterized in that, The oxide raw material powder is any one of indium tin oxide (ITO), indium cerium oxide (ICO), indium zinc oxide (IZO), indium gallium oxide (IGO), or indium tungsten oxide (IWO).

3. The method for preparing a highly uniform oxide target for reactive plasma deposition according to claim 2, characterized in that, The proportion of indium oxide in the oxide raw material powder is 80~99wt%.

4. The method for preparing a highly uniform oxide target for reactive plasma deposition according to claim 3, characterized in that, The cellulose-based pore-forming agent is any one or a combination of methylcellulose (MC), hydroxypropyl methylcellulose (HPMC), carboxymethyl cellulose (CMC), or microcrystalline cellulose.

5. The method for preparing a highly uniform oxide target for reactive plasma deposition according to claim 1, characterized in that, The fourth step of degreasing includes: In the first stage, the temperature is increased to 200-260℃ at a rate of 0.5-1.0℃ / min and held for 2-4 hours to completely remove moisture and low-boiling-point impurities. In the second stage, the temperature is increased to 300-350℃ at a rate of 0.2-0.5℃ / min and held for 4-8 hours to allow the PVA adhesive to completely decompose and slowly escape. In the third stage, the temperature is increased to 450-550℃ at a rate of 0.3-0.8℃ / min and held for 3-6 hours to allow the cellulose pore-forming agent to decompose uniformly and form the initial pore structure.

6. The method for preparing a highly uniform oxide target for reactive plasma deposition according to claim 1, characterized in that, In step one, the powder is first ball-milled until the particle size D50 is 0.5-2.0 μm and D90 ≤ 5.0 μm; then it is ball-milled again to disperse the powder until the particle size D50 is 0.5-2.0 μm and D90 ≤ 5.0 μm.

7. The method for preparing a highly uniform oxide target for reactive plasma deposition according to claim 1, characterized in that, The particles obtained in step two have a particle size of 50-150 μm and a loose packing density of 1.2-1.8 g / cm³.

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