A method for preparing a magnesium fluoride ceramic sputtering target

Abstract

The application relates to a preparation method of a magnesium fluoride ceramic sputtering target material, and belongs to the technical field of inorganic non-metal material preparation.The fine-grain isostatic pressing graphite die with a wall thickness to inner diameter ratio of 0.4-0.6 and a height to target material height ratio of 5-16 is designed, a composite structure of a BN coating or a graphite paper isolation layer and a molybdenum or tantalum foil heat layer is combined, and the radial temperature uniformity control of the magnesium fluoride target material is realized; the gradient particle size loading of coarse powder outside and fine powder inside, three-step gradient precise pressing and the synergistic process of high-temperature sintering and pressure relief are adopted, the cooling cracking bottleneck caused by high brittleness of the magnesium fluoride is broken through; the gradient temperature control of degassing preheating, medium-temperature transition and high-temperature sintering and the scheme of vacuum-high-purity argon atmosphere switching are matched, the target material with a density greater than 98% and without macroscopic cracks can be prepared, when the purity of the magnesium fluoride powder is greater than 99.9%, the maximum diameter of the target material can reach 220 mm, and the industry problem that the yield of the traditional hot pressing process is less than 70% is solved.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of inorganic non-metallic material preparation, and particularly relates to a preparation method of a magnesium fluoride ceramic sputtering target material. BACKGROUND

[0002] Magnesium fluoride has excellent optical properties, high thermal stability and chemical stability, high hardness and other physical and chemical properties. The chemical formula of magnesium fluoride is MgF2, the melting point is 1248℃, the density is 3.15g / cm 3 , has a tetragonal rutile (TiO2) crystal structure, and the space group is P42 / mnm (136). It has very excellent transmittance, low refractive index (n=1.38), and wide band gap (10.8eV) in the range from 120nm wavelength of vacuum ultraviolet to 80μm wavelength of infrared. In addition, the magnesium fluoride crystal also has birefringence performance and a high laser damage threshold. These excellent properties make magnesium fluoride often used as a surface passivation layer of semiconductor devices in the semiconductor industry to protect the chip from environmental moisture and ion pollution, especially stable in high temperature processes. In the optoelectronic industry, magnesium fluoride target material is often used to make protective film materials for optical electronic equipment, used on the surface of optical elements to prevent scratching or corrosion, commonly used in camera lenses, microscopes, laser devices, etc.

[0003] Preparation of MgF2 single crystal mainly adopts the Czochralski growth method and the dry pot lowering method (Xu Chao, Zhang Qinhui, Liu Xiaoyang, Liu Jianqiang, Shi Dawei, Zhang Yuntian, Zhen Xiheng. Growth of high-quality magnesium fluoride single crystal by the Czochralski method [J]. Journal of Artificial Crystals, 2017, 46:2304-2305).

[0004] Preparation of polycrystalline MgF2 ceramic mainly adopts hot-pressing sintering method, for example, CN110981484A discloses that first, nano-sized MgF2 powder is purified in a tube furnace at 540~580℃ for 3~9h, then a vacuum hot-pressing furnace is used to press at 540~640℃ and 400~550MPa to obtain nano-sized MgF2 transparent ceramic, and finally an annealing furnace is used to anneal at 500~560℃ for 1~3h, the obtained MgF2 transparent ceramic has uniform and small crystal grains (average≤100nm), the bending strength is≥140MPa, and the Vickers hardness is≥700kg / mm 2There is a certain transmittance (average > 40%) in the visible light band (350~770nm) and is especially suitable for mid-wave infrared window / casing materials. However, the key parameters such as sample size, mechanical properties, optical properties, and vacuum degree during preparation are not reported in the examples. CN115894033A discloses that the pre-sintered body of magnesium fluoride powder after pre-sintering at 1000~1200℃ is loaded into a metal jacket and subjected to hot isostatic pressing at 1000~1200℃, the pressure is 100~200MPa, the time is 1~5h, the density of the magnesium fluoride slow-cooled body prepared is more than 98%, the purity is more than 99.9%, the Vickers hardness is more than 300HV, and the diameter can reach more than 400mm. CN118955139A discloses a preparation method of magnesium fluoride target material, which is to press magnesium fluoride powder into a mold at a pressure of 30~40MPa, then heat the mold in a vacuum hot pressing furnace at an absolute vacuum degree of ≤10Pa, and heat at 400~500℃ and 850~930℃ in two stages, apply a pressure of 50~60MPa after heating for 5~10min in the second stage, release the pressure after the second stage heating is completed, and then process the magnesium fluoride target blank after cooling.

[0005] Comparing the above preparation methods, (1) the highest heating temperature adopted by different preparation methods varies greatly, from a minimum of 560 DEG C to a maximum of 1200 DEG C; (2) the pressure difference is large, from 550 MPa used at low temperature to 200 MPa of hot isostatic pressing, and CN118955139A patent also uses vacuum hot pressing furnace, but the pressure is only 50-60 MPa; (3) the performance difference is large, the hardness of the obtained magnesium fluoride covers 300-700 HV; (4) the effect of hot isostatic pressing is good, and it is also suitable for preparing large-size moderators, but the cost is high and the cycle is long; the efficiency of conventional vacuum hot pressing is relatively high, but the cracking risk caused by heating temperature, pressure and cooling is not considered; (5) the current technology does not fully consider the physical properties of magnesium fluoride, does not emphasize the bottleneck problem of preparing magnesium fluoride target, and does not propose measures to prevent magnesium fluoride target from cracking. Magnesium fluoride is a typical insulator, the thermal conductivity is low, and the thermal expansion coefficient and thermal conductivity of a-axis and c-axis are obviously anisotropic, and the apparent elastic limit is only 49.64 MPa, and the bending strength is generally less than 125-140 MPa, and the compressive strength at 900 DEG C is only about 15 MPa, therefore, the stress sensitivity of magnesium fluoride target in the preparation process is very strong, and there are two core contradictions of insulator heating and brittle material pressure sintering cracking; (6) the core principle of sintering material by using joule hot pressing furnace is to directly pass through the electrically conductive mold and the sample itself by using large current, and to sinter by using the resistance to generate joule heat, so the material has certain electrical conductivity and thermal conductivity, therefore, there are inherent contradictions and technical obstacles that cannot be overcome in the preparation of MgF2 ceramic brittle insulator target by using joule hot pressing furnace, such as poor electrical conductivity, which cannot be heated, and the need for rapid and efficient sintering, the need for pressure densification, and the risk of cracking under pressure. Therefore, there are few reports on the preparation of ceramic materials including magnesium fluoride by using joule hot pressing furnace.

[0006] In summary, in view of the problems of long preparation cycle, high cost, inadequate anti-cracking measures, lack of solutions for the characteristics of magnesium fluoride, and the fact that the existing technology cannot be directly applied to the joule hot pressing furnace, how to efficiently and high-quality prepare magnesium fluoride target by using joule hot pressing furnace is currently lacking in corresponding preparation technology at home and abroad. SUMMARY

[0007] The technical problem to be solved by the present application is to provide a preparation method of a magnesium fluoride ceramic sputtering target for solving the problems that MgF2 is difficult to be hot-pressed and prepared as an insulator and brittle material, and the deficiencies of the prior art.

[0008] To solve the above technical problems, the technical scheme adopted by the present application is as follows: a preparation method of a magnesium fluoride ceramic sputtering target, comprising the following steps:

[0009] S1, preparing raw material powder:

[0010] Magnesium fluoride powder with a purity better than 98% was used as the sintering raw material. The powder particle size was at least one of 200 mesh, 300 mesh, 400 mesh, and nano powder. The magnesium fluoride powder was weighed, then placed in a stainless steel pan, and then placed in a vacuum drying oven. The vacuum degree was evacuated to ≤5×10 at room temperature. -1 After Pa, heat at a heating rate of less than 20℃ / min, and dry at 200~350℃ for 0.5~1h for low-temperature dehydration, and dry at 500~600℃ for 2~4h for high-temperature dehydration to remove adsorbed air, moisture, water of crystallization, hydrogen fluoride, etc., to complete the preparation of raw material powder.

[0011] S2. Prepare the mold:

[0012] The graphite mold is designed with a cylindrical concave mold and a cylindrical convex mold. The ratio of the wall thickness to the inner diameter of the concave mold is 0.4 to 0.6, and the ratio of the height of the concave mold to the designed height of the target material is 5 to 16. The inner diameter of the concave mold is 2.0% to 3.5% larger than the designed diameter of the target material. The outer diameter of the convex mold is 1.4% to 3.2% larger than the designed diameter of the target material. Two molybdenum or tantalum foils with the same diameter as the inner diameter of the concave mold and a thickness of 0.15 to 0.5 mm are cut. Graphite paper with the same inner surface area as the concave mold is cut or the inner cavity of the concave mold is coated with BN.

[0013] S3. Loading:

[0014] Cover the surface of the inner cavity of the die with graphite paper or apply a BN coating to the inner cavity of the die to ensure that the graphite mold and magnesium fluoride powder do not come into direct contact. Place a layer of molybdenum or tantalum foil cut in step S2 between the bottom of the die and the graphite base. Then pour the raw material powder from step S1 into the graphite mold according to the particle size gradient, with coarse powder on the outside and fine powder on the inside. Place a layer of molybdenum or tantalum foil on top of the powder. Cover the outside of the graphite mold with a layer of heat-insulating asbestos felt. Insert the cylindrical punch into the cavity of the die. Place the loaded graphite mold into a vacuum Joule hot press furnace and apply a pre-pressure of 10-14 MPa. Close the furnace door and start evacuating the furnace body to complete the loading.

[0015] S4. Degassing and preheating:

[0016] When the vacuum degree inside the Joule hot press furnace is less than 5×10 -3 After Pa, reduce the pre-pressure to 0.5~1.0 MPa, start heating at a rate of 4~8℃ / min, and hold at 600℃ for at least 15 minutes, ensuring the vacuum level inside the furnace reaches ≤1×10⁻⁶. -2 After Pa, degassing and preheating are completed;

[0017] S5, Medium Temperature Transition:

[0018] Continuing to heat, the heating rate is 8~12℃ / min, when the temperature reaches 1100℃, the pressure is increased to 5MPa, 10MPa and 15MPa at 900℃, 1000℃ and 1100℃ respectively, and the vacuum degree in the furnace is ≤5×10 -2 Pa after the temperature transition at medium temperature is completed;

[0019] S6, high-temperature sintering:

[0020] Continuing to heat, the heating rate is 8~12℃ / min, when the temperature reaches 1130~1200℃, the pressure is increased to 25~30MPa, and the high-temperature sintering process is completed after 8~20min of holding;

[0021] S7, slow cooling:

[0022] The pressure is rapidly reduced to 0~5MPa, the cooling rate is controlled to be 3~5℃ / min, high-purity argon is filled at a flow rate of 2~3L / min and the pressure is increased to 50~80kPa in steps, then the gas filling is stopped, the temperature is reduced to 1000~950℃, the pressure is completely unloaded, and the slow cooling is completed;

[0023] S8, furnace cooling:

[0024] When the temperature is reduced to 800℃, the cooling speed is controlled to be ≤10℃ / min, the furnace cooling is completed after the temperature is reduced to 100℃ or below after cooling to 300℃;

[0025] S9, discharging:

[0026] The air is discharged to open the door to take out the graphite mold, the product is pressed out of the graphite mold by using a press, the graphite on the surface of the product is ground off by using fine sandpaper, and the preparation of the magnesium fluoride target material is completed.

[0027] Further, in step S1, the required mass of magnesium fluoride powder is weighed, and the required mass is equal to the product of the theoretical density and the theoretical volume corresponding to the increase of 2.0~3.5% in the diameter and thickness of the target material.

[0028] Further, in step S1, the purity of the magnesium fluoride powder can be selected to be not less than 98% and 99% of the industrial grade purity, 99.9% or 99.95% of the high-purity grade powder, and preferably, the purity of the magnesium fluoride powder is not less than 99.9%.

[0029] Further, in step S1, the impurity content of the magnesium fluoride powder satisfies: Al≤0.015%, Ba≤0.008%, Cu≤0.008%, Fe≤0.008%, Mn≤0.015%, Ca≤0.015%, Ti≤0.008%, Na≤0.02%, H2O≤1.0%.

[0030] Further, in step S1, the particle size of the magnesium fluoride powder is selected from 200 mesh, 300 mesh and 400 mesh, and the mass percentage of each particle size powder is 30% to 100%; or 5% to 20% of the magnesium fluoride nano-powder with a particle size less than 100 nm is added to the three particle size powders.

[0031] Further, in step S1, the limit vacuum degree of the vacuum drying furnace is ≤6.5×10 -2 Pa.

[0032] Further, in step S2, the graphite mold uses an isotropic fine-grained isostatic pressing graphite mold with a compressive strength of more than 150 MPa.

[0033] Further, in step S2, the graphite mold has an electrical conductivity of more than 1.5×10 4 S / m, a thermal conductivity of more than 120 W / (m·K), and an ash content of ≤200 ppm.

[0034] Further, in step S2, the graphite paper has a thickness of 0.1 to 0.2 mm, a carbon content of more than 99%, a tensile strength of ≥4.0 MPa, a sulfur content of ≤300 ppm, and a chlorine content of ≤35 ppm.

[0035] Further, in step S2, the BN coating is obtained by brushing, spraying or chemical vapor deposition after mixing BN powder with alcohol, and the content of BN is not less than 99.0%, the content of B2O3 is not higher than 0.5%, and the thickness of the coating is 30 to 60 μm.

[0036] Further, in step S3, the asbestos felt is a high-temperature asbestos felt with a thickness of ≥7 mm, and the size of the asbestos felt is determined according to the size of the outer surface of the sintering mold, the surface area of the unfolded asbestos felt needs to be greater than the surface area of the graphite mold, and the width of the asbestos felt is 3 to 7 mm higher than the axial height of the graphite mold to ensure that the outer surface of the mold is completely covered.

[0037] Further, in step S9, after the furnace is discharged, detection is further performed, the corresponding chemical composition, density and hardness of the product are measured, and the product is packaged and stored after analysis.

[0038] In summary, the beneficial effects of the present application are:

[0039] (1) The present application uses a vacuum Joule heat pressing furnace for sintering, and the rapid heating characteristics of the furnace make the graphite mold heat quickly, the preparation process is short, the preparation efficiency is high, the yield is high, the cost is greatly saved, and it is suitable for enterprise batch production.

[0040] (2) The innovation of the raw material powder selection of the application is that four specifications of powder particle size, namely 200 mesh, 300 mesh, 400 mesh and nano powder, are selected to obtain different surface energies, the temperature difference during heating and cooling of the target material is reduced by the combination and arrangement of the powders through the difference of the surface energies of the powders; a two-stage dehydration scheme for the magnesium fluoride raw material is designed, that is, low-temperature dehydration at 200-350 DEG C for 0.5-1 h and high-temperature dehydration at 500-600 DEG C for 2-4 h, so that the impurities such as adsorbed air, moisture, crystal water and hydrogen fluoride in the powder are effectively removed.

[0041] (3) The innovation of the multi-layer composite mold design of the application is that a graphite mold with high thermal conductivity, high melting point, low reactivity, high resistivity and low price is selected, an isotropic fine-grained isostatic pressing graphite mold with a compressive strength of more than 150 MPa is used, the temperature hysteresis in the central region is reduced, the thermal conductivity and electrical conductivity of the mold are improved, and the fluctuation range of the thermal conductivity and electrical conductivity of the mold is reduced; since the thermal expansion coefficient and thermal conductivity of magnesium fluoride in the a-axis and c-axis directions are quite different, a large internal stress is easily generated, and since the thermal conductivity of molybdenum and tantalum is higher than that of graphite, molybdenum or tantalum sheets are designed to be applied to the upper and lower ends of the powder to improve the speed and uniformity of the axial heat transfer, reduce the temperature difference and prevent local overheating; the inner cavity of the graphite mold is isolated from the magnesium fluoride raw material by using graphite paper or a micron-thick BN layer with high high-temperature stability to prevent the transition reaction between the graphite mold and the magnesium fluoride raw material to form a brittle Mg-C phase; the magnesium fluoride sintering will produce a shrinkage phenomenon, and the thermal expansion coefficient and cold shrinkage coefficient of the magnesium fluoride raw material are fully considered to design the graphite mold with an increased inner diameter size; the ratio relationship between the mold wall thickness and the inner diameter size, the mold height and the target thickness is limited, the heat storage, conduction and radiation capacity of the mold is enhanced, the uniformity of the target heating is improved, the temperature difference is reduced, and the internal stress in the target is effectively reduced.

[0042] (4) The innovation of the stepwise heating design of the application is that for the target with a relatively thin thickness, it is crucial to ensure that the entire compact is uniformly heated and pressed, otherwise, gradient stress and uneven density are easily generated. Since the band gap of MgF2 is as high as 6.82-11.8 eV, it is a typical insulator, and the room temperature resistivity is more than 10 14 Ω·cm, which means that at room temperature or even medium temperature, the current cannot directly pass through the MgF2 powder or compact; at the same time, the thermal conductivity of MgF2 is 0.3 W / (m·K), and the thermal diffusion coefficient is 8.8 mm 2 / s, so the thermal conductivity is also poor, which will exacerbate the temperature gradient and internal stress in different regions of the target; the core principle of the Joule heat sintering is to let a large current directly pass through the conductive mold and the sample itself, and use the resistance to generate Joule heat for sintering, so the material needs to have certain electrical conductivity and thermal conductivity, and the resistivity of MgF2 is more than 10 6Ω·m, it is unable to be sintered directly by Joule heat, thus, there is an insurmountable bottleneck problem in the preparation of MgF2 by using a Joule heat pressing furnace for sintering. According to the thermodynamic performance and electronic performance design of MgF2, the heating of the target material is divided into three stages of degassing preheating, medium-temperature transition and high-temperature sintering. The first stage is to complete degassing (air, H2O and hydrolysis product Mg(OH)F, etc.) under low pressure; the second stage makes full use of the characteristics that the ionic conductivity of magnesium fluoride is significantly improved and the plastic deformation ability is improved above 800 DEG C, and meanwhile, the uniformity of temperature and pressure is improved; the third stage uses high temperature and high pressure to overcome the disadvantages of low diffusion coefficient and relatively poor sintering activity of MgF2, and realizes the dense sintering close to the theoretical density; meanwhile, the target material is annealed by using the residual temperature after reducing the pressure.

[0043] (5) The innovation of the pressure design of the present application is reflected in that for brittle materials, the timing (temperature), size, uniformity and pressure release strategy of the applied pressure are extremely critical. If not careful, the pressure may cause the green compact to crack. According to calculation, the compressive strength of the green compact is less than 2 MPa, thus, the pressure cannot be greater than 1 MPa before heating to 600 DEG C, otherwise the green compact will directly break, but a pre-pressure is applied before heating to complete the initial powder forming; the plasticity of MgF2 is enhanced and the creep rate is improved when the temperature exceeds 800 DEG C, thus, the temperature is designed to be increased to more than 900 DEG C and then the pressure is increased in stages, so that the material has sufficient plastic deformation ability; but the compressive strength of MgF2 at 900 DEG C is only about 15 MPa, and by controlling the heating rate, heating temperature and pressure, the residual thermal stress can be reduced to about 8 MPa according to calculation, so that high-temperature cracking is avoided; the apparent elastic limit of MgF2 is 49.64 MPa, the bending strength is low (generally less than 125 MPa), the tensile strength is 50~80 MP and is highly dependent on the defect size and distribution in the material, thus, the pressure at the highest temperature is not more than 25 MPa.

[0044] (6) The innovation of the stage-by-stage cooling design of the present application is reflected in that both the thermal stress in the sintering process and the cooling stress are extremely easy to cause the brittle target material to crack. Since the thermal expansion coefficients of the a-axis and the c-axis of MgF2 are obviously anisotropic (alpha a =10.5x10 -6 / K, alpha c =18.9x10 -6 / K), and is prone to cracking due to internal stress during cooling, so the pressure is rapidly reduced to 0-5 MPa after sintering and heat preservation is completed; since the compressive strength of MgF2 at 900 DEG C is only about 15 MPa, the starting temperature of complete pressure relief is set to 1000-950 DEG C; the cooling rate is controlled by wrapping different thicknesses of asbestos felt outside the graphite mold and by applying a small current; in addition, MgF2 is prone to thermal decomposition in a vacuum environment above 1000 DEG C, and the introduction of high-purity argon can inhibit its decomposition to form impurities; and vacuum cooling mainly relies on radiation heat transfer, which can cause a steep temperature gradient between the surface and the center of the graphite mold, and the filling of argon can improve the dominance of axial heat exchange, making the stress distribution more uniform.

[0045] (7) The application designs a scheme for switching between vacuum and high-purity argon atmosphere: a high-vacuum environment is constructed during heating and heat preservation to exclude air, moisture, crystal water, hydrogen fluoride and the like attached to the powder; as the temperature rises, the vacuum degree is always better than 5x10 -2 Pa, reducing the possibility of reaction with residual atmosphere (O2, H2O) or graphite mold at high temperature to generate impurities (such as MgO), etc., ensuring that the purity of the target material is not less than the raw material; during cooling, micro-positive-pressure argon is filled to replace the uncontrollable thermal radiation gradient with controllable weak argon convection, preventing the thermal decomposition of MgF2, eliminating the risk of vacuum glow discharge between electrodes, and controlling the stress directionality of cooling.

[0046] (8) The size range of the MgF2 target material product manufactured by the application is Φ50.8-220mmx3-22mm, and the obtained product has a density of more than 98% and a hardness of more than 381.9HV. Compared with the cracking rate of more than 30% of the traditional hot pressing process, the cracking rate of the application is less than 5%.

[0047] (9) The preparation method of the application is also applicable to the production of other ceramic products similar to MgF2 in physical and chemical properties.

[0048] In summary, the present application has the advantages of fewer production processes, shorter production cycle, high preparation efficiency, low production cost and high yield; the present application realizes the radial temperature uniformity control of the magnesium fluoride target material by designing the fine-grain isostatic pressing graphite mold with a wall thickness to inner diameter ratio of 0.4-0.6 and a height to target material height ratio of 5-16, combining the inner lining BN coating or graphite paper isolation layer and the molybdenum or tantalum foil uniform heating layer; the gradient particle size loading of coarse powder outside and fine powder inside, the three-step gradient precise pressing (900 DEG C / 5MPa→1000 DEG C / 10MPa→1100 DEG C / 15MPa) and high-temperature sintering pressure relief (1130-1200 DEG C holding pressure 20-25MPa→gradient relief to 0MPa before cooling to 1000-950 DEG C) synergistic process breaks through the cooling cracking bottleneck caused by high brittleness of magnesium fluoride; in combination with the gradient temperature control of degassing preheating, medium temperature transition and high temperature sintering and the scheme of vacuum-high purity argon atmosphere switching, the target material with a density of >98% and without macroscopic cracks can be prepared, and when the purity of magnesium fluoride powder is >99.9%, the maximum diameter of the target material can reach 220mm, solving the industry problem of a yield of <70% in the traditional hot pressing process. BRIEF DESCRIPTION OF DRAWINGS

[0049] The present application will be described in detail below with reference to the accompanying drawings and specific examples, and the advantages and implementation modes of the present application will be more obvious, wherein the contents shown in the drawings are only used to explain the present application and do not constitute any sense of limitation on the present application, and in the drawings:

[0050] Figure 1 It is a schematic diagram of the implementation steps of the technical scheme of the present application.

[0051] Figure 2 It is a scanning electron microscope secondary electron image photograph of the surface of the target material taken out after completing the degassing preheating in Example 1 of the present application.

[0052] Figure 3 It is a macroscopic photograph of the magnesium fluoride target material obtained by sintering in Example 1 of the present application.

[0053] Figure 4 It is a result graph of the hardness test of the target material using a Vickers hardness tester in Example 1 of the present application.

[0054] Figure 5 It is a scanning electron microscope photograph of the magnesium fluoride target material obtained by sintering in Example 1 of the present application.

[0055] Figure 6 It is an energy spectrum graph of the magnesium fluoride target material obtained by sintering in Example 1 of the present application.

[0056] Figure 7 It is a macroscopic photograph of the magnesium fluoride target material obtained by sintering in Example 2 of the present application.

[0057] Figure 8The result graph of testing the hardness of the target material by using a Vickers hardness tester in Example 2 of the present application.

[0058] Figure 9 The scanning electron microscope photo of the magnesium fluoride target material sintered in Example 2 of the present application.

[0059] Figure 10 The energy spectrum graph of the magnesium fluoride target material sintered in Example 2 of the present application.

[0060] Figure 11 The macro photo of the magnesium fluoride target material sintered in Example 3 of the present application.

[0061] Figure 12 The result graph of testing the hardness of the target material by using a Vickers hardness tester in Example 3 of the present application.

[0062] Figure 13 The X-ray diffraction graph of the magnesium fluoride target material sintered in Example 3 of the present application.

[0063] Figure 14 The result graph of testing the hardness of the target material by using a Vickers hardness tester in Example 4 of the present application.

[0064] Figure 15 The X-ray diffraction graph of the magnesium fluoride target material sintered in Example 4 of the present application.

[0065] Figure 16 The scanning electron microscope photo of the magnesium fluoride target material sintered in Example 5 of the present application.

[0066] Figure 17 The result graph of testing the hardness of the target material by using a Vickers hardness tester in Example 5 of the present application. DETAILED DESCRIPTION

[0067] In order to make the person skilled in the art better understand the technical solutions of the present application, the present application will be further described in detail below in combination with the best embodiments.

[0068] As Figure 1 shown:

[0069] Example 1

[0070] Preparation of the Φ50.8mmx3mm magnesium fluoride ceramic sputtering target material:

[0071] S1, preparing raw material powder:

[0072] The magnesium fluoride powder with purity better than 98% is used as the sintering raw material, the powder particle size is 200 meshes, according to the product specification Φ50.8mmx3mm, 20.3g of magnesium fluoride powder is weighed by a balance, then the magnesium fluoride powder is put into a stainless steel tray, and then the magnesium fluoride powder is put into a vacuum drying oven, the vacuum degree is extracted to 5x10-1 After Pa, the material is heated at a rate of 19℃ / min and then dried at 200℃ for 0.5h for low-temperature dehydration and at 500℃ for 2h for high-temperature dehydration. Vacuum is continuously applied during the heating process to remove adsorbed air, moisture, water of crystallization, hydrogen fluoride, etc., thus completing the preparation of the raw material powder.

[0073] S2. Prepare the mold:

[0074] The graphite mold structure is designed using isotropic, fine-grained isostatic graphite with a compressive strength exceeding 150 MPa. The cylindrical die has a wall thickness of 20.7 mm (0.4 times the inner diameter Φ51.8 mm), a height of 48 mm (16 times the target material's designed height of 3 mm), and an inner diameter of Φ51.8 mm (2.0% larger than the target material's designed diameter Φ50.8 mm). The cylindrical punch has an outer diameter of Φ51.5 mm (1.4% larger than the target material's designed diameter Φ50.8 mm). Two 0.15 mm thick molybdenum foils with the same diameter as the die's inner diameter Φ51.8 mm are cut. One 0.1 mm thick sheet of graphite paper with the same surface area as the die's inner surface is also cut, completing the preparation of the graphite mold.

[0075] S3. Loading:

[0076] First, cover the surface of the inner cavity of the concave mold with graphite paper to ensure that the graphite mold and magnesium fluoride powder do not come into direct contact. Place a layer of molybdenum foil cut in step S2 between the bottom of the concave mold and the graphite base. Then, pour the raw material powder from step S1 into the graphite mold, and place a layer of molybdenum foil on top of the powder. Cover the outside of the graphite mold with a 7mm thick layer of thermal insulation asbestos felt, with the width of the asbestos felt being 3mm higher than the axial height of the graphite mold. Then, insert the cylindrical punch into the cavity of the concave mold. After placing the loaded graphite mold into the vacuum Joule hot press furnace, apply a pre-pressure of 10MPa, close the furnace door, and begin vacuuming the furnace body to complete the loading.

[0077] S4. Degassing and preheating:

[0078] When the vacuum degree inside the Joule hot press furnace is less than 5×10 -3 After Pa, the pre-pressure is reduced to 0.5 MPa, and heating begins at a rate of 8℃ / min. When the temperature reaches 600℃, it is held for 15 minutes, and the vacuum degree inside the furnace reaches 1×10⁻⁶. -2 After Pa, degassing and preheating are completed.

[0079] like Figure 2 As shown, although the target material is basically dense, the powder particles are not continuously and densely bonded, which also proves that it is insufficient to sinter magnesium fluoride targets at temperatures below 600℃.

[0080] S5, medium temperature transition:

[0081] After completing step S4, continue to increase the temperature at a heating rate of 12℃ / min, and when the temperature reaches 1100℃, keep the temperature for 5min, while increasing the pressure to 5MPa, 10MPa and 15MPa at 900℃, 1000℃ and 1100℃ respectively in three steps, and when the vacuum degree in the furnace reaches 5x10 -2 Pa, complete the medium temperature transition.

[0082] S6, high temperature sintering:

[0083] After completing step S5, continue to increase the temperature at a heating rate of 12℃ / min, and when the temperature reaches 1130℃, increase the pressure to 25MPa, keep the temperature for 8min, and then complete the high temperature sintering process.

[0084] S7, slow cooling:

[0085] After completing step S6, rapidly decrease the pressure to 5MPa, control the cooling rate to be 5℃ / min, while filling high-purity argon at a flow rate of 3L / min and stepwise increasing the pressure to 50kPa, then stop the argon filling, decrease the temperature to 950℃, completely unload the pressure, and complete the slow cooling.

[0086] S8, furnace cooling:

[0087] When the temperature in step S7 decreases to 800℃, control the cooling rate to be 10℃ / min, and when the temperature decreases to 300℃, complete the furnace cooling by cooling to below 100℃ and then unloading the product.

[0088] S9, unloading and detection:

[0089] After completing the cooling in step S8, unload the graphite mold by releasing the pressure and opening the furnace door, press the product out of the graphite mold using a press, grind the graphite on the surface of the product using fine sandpaper, and measure the chemical composition, density and hardness of the product, and then package the product into the warehouse after analysis, and complete the preparation of the magnesium fluoride target material.

[0090] For example, Figure 3As shown, the sintered magnesium fluoride target material of Example 1 has no cracks; according to the national standard of magnesium fluoride for coating GB / T 31860-2015, the mass percentage of elements in the magnesium fluoride target material is tested using a Plasma 2000 type inductively coupled plasma atomic emission spectrometer combined with an ONH3000 type oxygen-nitrogen-hydrogen analyzer, containing 0.06% Al, 0.02% Ba, 0.015% Cu, 0.046% Fe, 0.05% Mn, 0.085% Ca, 0.04% Ti, 0.08% Na, 0.12% O, and 99.1% MgF2; the density of the magnesium fluoride target material is tested using a DJ-600Te digital solid-powder integrated densimeter, reaching 98.4% of the density 3.15 g / cm 3 measured in the powder diffraction card (PDF 00-006-0290). 3

[0091] As shown in Figure 4 , the hardness of the target material is tested using a HVS-10Z-PC type Vickers hardness tester, reaching 381.9 HV3.0.

[0092] As shown in Figure 5 , the surface of the unpolished target material is directly observed using a S-3400N type scanning electron microscope, and the surface is dense without microcracks.

[0093] As shown in Figure 6 , the elements on the surface of the target material are tested using a 51-ADD0009 type energy spectrometer attached to the scanning electron microscope, and the main elements are F and Mg, and the content of the remaining impurity elements is not obvious.

[0094] Example 2

[0095] Preparation of a Φ50.8mm×5mm magnesium fluoride ceramic sputtering target material:

[0096] S1, prepare raw material powder:

[0097] Magnesium fluoride powder with a purity of more than 99% is used as the sintering raw material, and the powder particle size is 300 meshes. According to the product specification Φ50.8mm×5mm, 35.4g of magnesium fluoride powder is weighed by a balance, and then the magnesium fluoride powder is placed in a stainless steel tray and placed in a vacuum drying oven. After the vacuum degree is extracted to 4×10 -1 Pa at room temperature, it is heated at a heating rate of 18℃ / min, and low-temperature dehydration is performed at 300℃ for 40min, and high-temperature dehydration is performed at 560℃ for 3h, to remove adsorbed air, moisture, crystal water, hydrogen fluoride, etc., and complete the preparation of the raw material powder.

[0098] S2, prepare the mold:

[0099] ​The structure of the graphite mold is designed, the graphite mold uses the isostatic fine-grained graphite mold with a compressive strength of more than 150 MPa, the wall thickness of the cylindrical concave mold is 31.5 mm (the ratio to the inner diameter is 0.6), the height of the concave mold is 50 mm (the ratio to the designed height of the target material 5 mm is 10 times), the inner diameter size of the concave mold is Φ52.6 mm (3.5% larger than the designed diameter of the target material Φ50.8); the outer diameter size of the cylindrical convex mold is Φ52.3 mm (3.2% larger than the designed diameter); two pieces of tantalum foil with a thickness of 0.2 mm and a diameter same as the inner diameter size of the concave mold Φ52.6 are cut; the BN coating with a thickness of 30 μm is brushed on the inner cavity of the concave mold, and the preparation of the graphite mold is completed.

[0100] S3, charging:

[0101] The tantalum foil cut in step S2 is placed between the bottom of the concave mold and the graphite base, the raw material powder in step S1 is poured into the graphite mold, and one layer of tantalum foil is placed on the top of the powder; the graphite mold is covered with a layer of asbestos felt with a thickness of 8 mm for heat preservation, the width of the asbestos felt is 4 mm higher than the axial height of the graphite mold, and the cylindrical convex mold is inserted into the mold cavity of the concave mold; the graphite mold with the charge is placed in the vacuum joule heat pressing furnace, a pre-pressure of 14 MPa is applied, the furnace door is closed, the furnace body is vacuumized, and the charging is completed.

[0102] S4, degassing and preheating:

[0103] When the vacuum degree in the joule heat pressing furnace is less than 5×10 -3 Pa, the pre-pressure is reduced to 0.8 MPa, the temperature is raised at a rate of 6 ℃ / min, the temperature is kept at 600 ℃ for 16 min, and the vacuum degree in the furnace is kept at 1×10 -2 Pa, and the degassing and preheating are completed.

[0104] S5, medium temperature transition:

[0105] After step S4 is completed, the temperature is continuously raised at a rate of 10 ℃ / min, the temperature is kept at 1100 ℃ for 330 s, the pressure is increased to 5 MPa, 10 MPa and 15 MPa at 900 ℃, 1000 ℃ and 1100 ℃ respectively in three times, and the vacuum degree in the furnace is kept at 4×10 -2 Pa, and the medium temperature transition is completed.

[0106] S6, high temperature sintering:

[0107] After step S5 is completed, the temperature is continuously raised at a rate of 10 ℃ / min, the pressure is increased to 28 MPa when the temperature reaches 1150 ℃, and the high temperature sintering process is completed after keeping the temperature for 9 min.

[0108] S7, slow cooling:

[0109] After completing step S6, the pressure is rapidly reduced to 3 MPa, the cooling rate is controlled at 4 °C / min, and high-purity argon gas is introduced at a flow rate of 2 L / min and pressurized stepwise to 60 kPa before the gas introduction is stopped. After cooling to 960 °C, the pressure is completely released to complete the slow cooling.

[0110] S8. Cooling in the furnace:

[0111] When the temperature in step S7 drops to 800℃, the cooling rate is controlled at 9℃ / min. After cooling to 300℃, the furnace is cooled to below 100℃ before the furnace is removed, thus completing the furnace cooling process.

[0112] S9. Unloading and Testing:

[0113] After cooling in step S8, the furnace door is opened to release the gas and the graphite mold is removed. The product is pressed out of the graphite mold using a press, and the graphite on the surface of the product is removed by sandpaper. The chemical composition, density and hardness of the product are measured. After the analysis is qualified, it is packaged and stored to complete the preparation of magnesium fluoride target material.

[0114] like Figure 7 As shown, the sintered magnesium fluoride target material was free of cracks. According to the national standard GB / T 31860-2015 for magnesium fluoride used in coating, the mass percentage of elements in the magnesium fluoride target material was tested using a Plasma 2000 inductively coupled plasma atomic emission spectrometer combined with an ONH3000 oxygen, nitrogen, and hydrogen analyzer. The results showed it contained 0.05% Al, 0.01% Ba, 0.010% Cu, 0.035% Fe, 0.02% Mn, 0.053% Ca, 0.02% Ti, 0.05% Na, 0.10% O, and 99.5% MgF2. The density of the manganese target material was measured to be 3.13 g / cm³ using a DJ-600Te digital display solid-powder integrated density meter. 3 The density reached 3.15 g / cm³, as measured in the powder diffraction card (PDF 00-006-0290). 3 99.4%.

[0115] like Figure 8 As shown, the hardness of the target material tested using a Vickers hardness tester of model HVS-10Z-PC reached 449.9HV3.0.

[0116] like Figure 9 As shown, the surface of the unpolished target material was directly observed using a scanning electron microscope of model S-3400N. The surface was dense and free of microcracks.

[0117] like Figure 10The main elements are F and Mg, and the content of other impurity elements is not obvious.

[0118] Example 3

[0119] Preparation of Φ101.6mm*6.5mm magnesium fluoride ceramic sputtering target:

[0120] S1, preparing raw material powder:

[0121] The magnesium fluoride powder with a purity of more than 99.9% is used as the sintering raw material. Two specifications of powder are selected: 400 mesh powder with a mass percentage of 95%, and nano-powder with a mass percentage of 5%. According to the product specification Φ101.6mm*6.5mm, the total mass of the magnesium fluoride powder is 177.9g, which is weighed by a balance. Then the magnesium fluoride powder of two particle sizes is mixed and placed in a stainless steel tray, and then placed in a vacuum drying oven. The vacuum degree is extracted to more than 8*10 -2 Pa, and heated at a heating rate of 10℃ / min, and low-temperature dehydration is carried out at 350℃ for 1h, and high-temperature dehydration is carried out at 600℃ for 3h, so as to remove the adsorbed air, water, crystal water, hydrogen fluoride and the like, and complete the preparation of the raw material powder.

[0122] S2, preparing the mold:

[0123] The structure of the graphite mold is designed. The isotropic fine-grained isostatic pressing graphite mold with a compressive strength of more than 150MPa is used. The wall thickness of the cylindrical concave mold is 52.1mm (the ratio to the inner diameter is about 0.5), the height of the concave mold is 52mm (the ratio to the designed height of the target material is 8), the inner diameter of the concave mold is Φ104.1mm (2.5% larger than the designed diameter of the target material), the outer diameter of the cylindrical convex mold is Φ103.6mm (2.0% larger than the designed diameter of the target material), two pieces of molybdenum foil with a thickness of 0.3mm and a diameter of the same as the inner diameter of the concave mold are cut, and one piece of graphite paper with a thickness of 0.2mm and a surface area the same as the inner surface area of the concave mold is cut, and the preparation of the graphite mold is completed.

[0124] S3, loading:

[0125] Firstly, the surface of the inner cavity of the concave die is covered with graphite paper to ensure that the graphite die has no direct contact with the magnesium fluoride powder; a layer of molybdenum foil cut in step S2 is placed between the bottom of the concave die and the graphite base, then the raw material powder in step S1 is poured into the graphite die, and then a layer of molybdenum foil is placed on the top of the powder; a layer of asbestos felt with a thickness of 10 mm is sleeved outside the graphite die for heat preservation, the width of the asbestos felt is 5 mm higher than the axial height of the graphite die, and then the cylindrical punch is inserted into the cavity of the concave die; after the graphite die with the loaded material is placed in the vacuum Joule heat pressing furnace, a pre-pressure of 14 MPa is applied, the door of the furnace is closed, the furnace body is vacuumized, and the loading is completed.

[0126] S4, degassing and preheating:

[0127] When the vacuum degree in the Joule heat pressing furnace is less than 5x10 -3 Pa, the pre-pressure is reduced to 1.0 MPa, the temperature starts to rise at a rate of 5℃ / min, and when the temperature reaches 600℃, the vacuum degree in the furnace reaches 9x10 -3 Pa, and the degassing and preheating are completed.

[0128] S5, medium temperature transition:

[0129] After step S4 is completed, the temperature continues to rise at a rate of 9℃ / min, and when the temperature reaches 1100℃, the pressure is increased to 5 MPa, 10 MPa and 15 MPa at 900℃, 1000℃ and 1100℃ respectively in three times, and when the vacuum degree in the furnace reaches 3x10 -2 Pa, the medium temperature transition is completed.

[0130] S6, high temperature sintering:

[0131] After step S5 is completed, the temperature continues to rise at a rate of 9℃ / min, and when the temperature reaches 1200℃, the pressure is increased to 30 MPa, and after 12 min of holding, the high temperature sintering process is completed.

[0132] S7, slow cooling:

[0133] After step S6 is completed, the pressure is quickly reduced to 1 MPa, the cooling rate is controlled at 3℃ / min, high-purity argon is filled at a flow rate of 3 L / min and the pressure is increased to 80 kPa in steps, and then the gas filling is stopped, the temperature is reduced to 1000℃, and then the pressure is completely removed, and the slow cooling is completed.

[0134] S8, furnace cooling:

[0135] When the temperature of step S7 is reduced to 800℃, the cooling speed is controlled at 8℃ / min, and when the temperature is cooled to 300℃, the furnace cooling is completed after the temperature is cooled to below 100℃ and the furnace is discharged.

[0136] S9. Unloading and Testing:

[0137] After cooling in step S8, the furnace door is opened to release the gas and the graphite mold is removed. The product is pressed out of the graphite mold using a press, and the graphite on the surface of the product is removed by sandpaper. The chemical composition, density and hardness of the product are measured. After the analysis is qualified, it is packaged and stored to complete the preparation of magnesium fluoride target material.

[0138] like Figure 11 As shown, the sintered magnesium fluoride target has a smooth surface without cracks. According to the national standard GB / T 31860-2015 for magnesium fluoride for coating, the mass percentage of elements in the magnesium fluoride target was tested using a Plasma 2000 inductively coupled plasma atomic emission spectrometer combined with an ONH3000 oxygen, nitrogen, and hydrogen analyzer. The results showed it contained 0.014% Al, 0.008% Ba, 0.008% Cu, 0.010% Fe, 0.014% Mn, 0.016% Ca, 0.009% Ti, 0.019% Na, 0.07% O, and 99.8% MgF2. The density of the manganese target was measured to be 3.14 g / cm³ using a DJ-600Te digital display solid-powder integrated density meter. 3 It reaches the theoretical density (3.15 g / cm³). 3 99.7% of ).

[0139] like Figure 12 As shown, the hardness of the target material tested using a Vickers hardness tester of model HVS-10Z-PC reached 469.0 HV3.0;

[0140] like Figure 13 As shown, the X-ray diffraction pattern of the target material was obtained by directly testing the surface using a Rigaku Dmax 2500PC X-ray diffractometer. The sample is composed of pure MgF2 with a tetragonal structure of space group P42 / mnm(136). The lattice constants were calculated using Dicvol software to be a = 4.6146 Å, c = 3.0491 Å, and the unit cell volume was 64.93 Å. 3 The standard data in powder diffraction card PDF00-041-1443 are a=4.62Å, c=3.0509Å, and the unit cell volume is 65.12Å. 3 Slightly smaller.

[0141] Example 4

[0142] Preparation of Φ152.4mm×16mm magnesium fluoride ceramic sputtering target:

[0143] S1. Prepare the raw material powder:

[0144] The magnesium fluoride powder with purity better than 99.95% is selected as the sintering raw material. Four specifications of magnesium fluoride powder are selected, i.e. 200 mesh, 300 mesh and 400 mesh magnesium fluoride powder with a mass percentage of 30% and 10% magnesium fluoride nanopowder with a particle size of less than or equal to 100 nm. According to the product specification Φ152.4mm×16mm, the total mass of the magnesium fluoride powder is 994.9g, which is weighed by a balance. Then, the 10% magnesium oxide nanopowder is evenly divided into three equal parts and mixed with the three kinds of particle size powders. The magnesium fluoride powders of different particle sizes are respectively placed in a stainless steel tray and then placed in a vacuum drying oven. After the vacuum degree is extracted to better than 6.5×10 -2 Pa at room temperature, the temperature is heated at a rate of 10℃ / min, and low-temperature dehydration is performed at 350℃ for 1h and high-temperature dehydration is performed at 600℃ for 4h, so as to remove the adsorbed air, water, crystal water, hydrogen fluoride and the like, and complete the preparation of the raw material powder.

[0145] S2, mold preparation:

[0146] The structure of the graphite mold is designed. The wall thickness of the cylindrical concave mold is 70.6mm (the ratio to the inner diameter is 0.45), the height of the concave mold is 80mm (5 times the design height of 16mm of the target material), and the inner diameter of the concave mold is Φ157.0mm (3% larger than the design diameter of the target material). The outer diameter of the cylindrical convex mold is 156.8mm (2.9% larger than the design diameter of the target material). Two pieces of tantalum foil with a diameter of Φ157.0mm and a thickness of 0.4mm are cut. The inner cavity of the concave mold is sprayed with a BN coating with a thickness of 60μm to complete the preparation of the graphite mold.

[0147] S3, loading:

[0148] A layer of tantalum foil cut in step S2 is placed between the bottom of the concave mold and the graphite base. The raw material powder in step S1 is poured into the graphite mold according to the particle size gradient, i.e. the coarse powder is poured into the outer side and the fine powder is poured into the inner side. A layer of tantalum foil is placed on the top of the powder. A layer of asbestos felt with a thickness of 10mm is wrapped outside the graphite mold for heat preservation. The width of the asbestos felt is 7mm higher than the axial height of the graphite mold. The cylindrical convex mold is inserted into the mold cavity of the concave mold. The graphite mold loaded with the material is placed in the vacuum joule heat pressing furnace, and a pre-pressure of 12MPa is applied. The furnace door is closed, and the furnace body is vacuumed to complete the loading.

[0149] S4, degassing and preheating:

[0150] When the vacuum degree in the joule heat pressing furnace is less than 5×10 -3 Pa, the pre-pressure is reduced to 0.5MPa, and the temperature is increased at a rate of 4℃ / min. When the temperature reaches 600℃, the temperature is maintained for 20min. When the vacuum degree in the furnace reaches 8×10 -3 Pa, the degassing and preheating are completed.

[0151] S5, medium temperature transition:

[0152] After completing step S4, continue to increase the temperature at a heating rate of 8°C / min, and when the temperature reaches 1100°C, keep it for 8 min, while increasing the pressure to 5 MPa, 10 MPa and 15 MPa at 900°C, 1000°C and 1100°C respectively in three steps, and complete the medium temperature transition when the vacuum degree in the furnace is less than 5x10 -2 Pa.

[0153] S6, high temperature sintering:

[0154] After completing step S5, continue to increase the temperature at a heating rate of 8°C / min, and when the temperature reaches 1150°C, increase the pressure to 30 MPa, and complete the high temperature sintering process after keeping it for 20 min.

[0155] S7, slow cooling:

[0156] After completing step S6, quickly reduce the pressure to 0 MPa, control the cooling rate to be 3°C / min, and stop the gas filling after filling high-purity argon at a flow rate of 2 L / min and increasing the pressure to 70 kPa in steps, and complete the slow cooling when the temperature is reduced to 950°C.

[0157] S8, furnace cooling:

[0158] When the temperature of step S7 is reduced to 800°C, control the cooling speed to be 5-8°C / min, and complete the furnace cooling after cooling to 300°C and then to below 100°C.

[0159] S9, furnace discharge and detection:

[0160] After completing the cooling of step S8, discharge the gas, open the furnace door and take out the graphite mold; use a press to press out the product from the graphite mold, grind off the graphite on the surface of the product using fine sandpaper, and measure the chemical composition, density and hardness of the product, and package it into the warehouse after analysis and qualification, to complete the preparation of the magnesium fluoride target material.

[0161] According to the national standard GB / T 31860-2015 for magnesium fluoride for coating, use a Plasma 2000 type inductively coupled plasma atomic emission spectrometer combined with an ONH3000 type oxygen-nitrogen-hydrogen analyzer to test the mass percentage of elements in the magnesium fluoride target material, containing 0.006% Al, 0.005% Ba, 0.005% Cu, 0.006% Fe, 0.008% Mn, 0.012% Ca, 0.006% Ti, 0.014% Na, 0.02% O, and 99.9% MgF2; use a DJ-600Te digital solid-powder integrated densimeter to test the density of the manganese target material, which is 3.14 g / cm 3, 99.7% of the theoretical density (3.15 g / cm 3 ).

[0162] As shown in FIG. 5, the hardness of the target material was tested using a Vickers hardness tester with a model number of HVS-10Z-PC, reaching 558.3 HV5. Figure 14

[0163] As shown in FIG. 6, the surface of the target material was directly tested using an X-ray diffractometer with a model number of Rigaku Dmax 2500PC, obtaining an X-ray diffraction pattern, and the sample was composed of pure MgF2 with a tetragonal structure of a space group of P42 / mnm (136). Figure 15 Using Dicvol software, the lattice constant thereof was calculated to be a = 4.6207 Å, c = 3.0531 Å, and a unit cell volume of 65.19 Å 3 . The standard data in the powder diffraction card PDF 00-041-1443 were a = 4.62 Å, c = 3.0509 Å, and a unit cell volume of 65.12 Å 3 , which was slightly larger.

[0164] Example 5

[0165] Preparation of a Φ220 mm x 22 mm magnesium fluoride ceramic sputtering target:

[0166] S1, preparing raw material powder:

[0167] Magnesium fluoride powder with a purity of more than 99.9% was used as a sintering raw material, and three specifications of powder particle sizes of 300 mesh, 400 mesh, and nano powder with mass percentages of 40%, 40%, and 20%, respectively, were selected. According to the product specification Φ220 mm x 22 mm, the total mass of the magnesium fluoride powder was weighed to be 2878.4 g using a balance, and then the 20% nano powder was equally divided into two equal parts and mixed with the two kinds of particle size powders, respectively. Then, the magnesium fluoride powders with different particle sizes were respectively placed in a stainless steel tray, and then placed in a vacuum drying oven. After the vacuum degree was extracted to be better than 2 x 10 -1 Pa at room temperature, heating was performed at a heating rate of 10 ℃ / min, and low-temperature dehydration was performed at 300 ℃ for 1 h, and high-temperature dehydration was performed at 600 ℃ for 4 h, to remove adsorbed air, water, crystal water, hydrogen fluoride, etc., and to complete the preparation of the raw material powder.

[0168] S2, preparing a mold:

[0169]

[0170] ​​The structure of the graphite die is designed, the wall thickness of the cylindrical female die is 91.1 mm (the ratio to the inner diameter is 0.4), the height of the female die is 110 mm (the ratio to the designed height of the target material is 5.0), the inner diameter size of the female die is Φ227.7 mm (3.5% larger than the designed diameter of the target material), the outer diameter size of the cylindrical male die is Φ227.0 mm (3.2% larger than the designed diameter of the target material), two molybdenum foils with a diameter same as the inner diameter size of the female die and a thickness of 0.5 mm are cut, the inner cavity of the female die is coated with a BN coating by a thermal chemical vapor deposition process, and the thickness of the BN coating is 40 μm, so as to complete the preparation of the graphite die.

[0171] S3, charging:

[0172] A layer of the molybdenum foil cut in step S2 is placed between the bottom of the female die and the graphite base, the raw material powder in step S1 is poured into the graphite die according to the powder particle size gradient, the coarse powder is poured into the outer side, the fine powder is poured into the inner side, a layer of the molybdenum foil is placed on the top of the powder, a layer of the asbestos felt with a thickness of 14 mm is sleeved on the outside of the graphite die for heat preservation, the width of the asbestos felt is 7 mm higher than the axial height of the graphite die, and the cylindrical male die is inserted into the cavity of the female die; the graphite die with the charge is placed into the vacuum Joule hot pressing furnace, a pre-pressure of 14 MPa is applied, the door of the furnace is closed, the furnace body is vacuumized, and the charging is completed.

[0173] S4, degassing and preheating:

[0174] When the vacuum degree in the Joule hot pressing furnace is less than 5×10 -3 Pa, the pre-pressure is reduced to 0.5 MPa, the temperature is increased at a rate of 4 ℃ / min, the temperature is kept at 600 ℃ for 18 min, the vacuum degree in the furnace is less than 5×10 -3 Pa, and the degassing and preheating are completed.

[0175] S5, medium-temperature transition:

[0176] After step S4 is completed, the temperature is continuously increased at a rate of 8 ℃ / min, the temperature is kept at 1100 ℃ for 10 min, the pressure is increased to 5 MPa, 10 MPa and 15 MPa at 900 ℃, 1000 ℃ and 1100 ℃ respectively in three times, and the vacuum degree in the furnace is 5×10 -2 Pa, and the medium-temperature transition is completed.

[0177] S6, high-temperature sintering:

[0178] After step S5 is completed, the temperature is continuously increased at a rate of 8 ℃ / min, the pressure is increased to 30 MPa when the temperature reaches 1150 ℃, and the high-temperature sintering process is completed after keeping the temperature for 20 min.

[0179] S7, slow cooling:

[0180] After completing step S6, the pressure is rapidly reduced to 0 MPa, the cooling rate is controlled at 3℃ / min, and high-purity argon gas is introduced at a flow rate of 3L / min and pressurized stepwise to 80kPa before stopping the gas introduction. The temperature is then reduced to 950℃ to complete the slow cooling.

[0181] S8. Cooling in the furnace:

[0182] When the temperature in step S7 drops to 800℃, the cooling rate is controlled at 6℃ / min. After cooling to 300℃, the furnace is cooled to below 100℃ before the furnace is removed, thus completing the furnace cooling process.

[0183] S9. Unloading and Testing:

[0184] After cooling in step S8, the furnace door is opened to release the gas and the graphite mold is removed. The product is pressed out of the graphite mold using a press, and the graphite on the surface of the product is removed by sandpaper. The chemical composition, density and hardness of the product are measured. After the analysis is qualified, it is packaged and stored to complete the preparation of magnesium fluoride target material.

[0185] like Figure 16 As shown, the sintered magnesium fluoride target material has no cracks on its surface, and no microcracks are found when it is directly observed under a scanning electron microscope of model S-3400N.

[0186] like Figure 17 As shown, the hardness of the target material tested using a Vickers hardness tester of model HVS-10Z-PC reached 606.6HV5.

[0187] The embodiments of the present invention have been described in detail above, but the content described is only a preferred embodiment of the present invention and should not be considered as limiting the scope of the present invention. All equivalent changes and improvements made within the scope of the present invention should still fall within the scope of the present invention.

Claims

1. A method of producing a ceramic magnesium fluoride sputtering target, characterized by: The method comprises the following steps: S1, preparing raw material powder: magnesium fluoride powder with purity better than 98% as sintering raw material, powder particle size is at least one of 200 mesh, 300 mesh, 400 mesh and nano powder, after weighing, put into vacuum drying oven, vacuumize to ≤5×10 -1 Pa, heat at a temperature rising rate lower than 20 ℃ / min, dry at 200~350 ℃ for 0.5~1h to perform low temperature dehydration, dry at 500~600 ℃ for 2~4h to perform high temperature dehydration, to obtain raw material powder; S2, preparing a mold: using a graphite mold comprising a cylindrical concave mold and a cylindrical convex mold; S3, loading: covering the inner cavity of the concave mold with graphite paper or a BN coating, placing a molybdenum or tantalum foil between the bottom of the concave mold and a graphite base, loading the raw material powder of step S1 into the graphite mold in a gradient, covering the raw material powder with a molybdenum or tantalum foil, wrapping the graphite mold with an asbestos felt, and then inserting the cylindrical convex mold into the concave mold; after the loaded graphite mold is placed into a vacuum Joule heat pressing furnace, a pre-pressure of 10-14 MPa is applied, the furnace body is vacuumized, and the loading is completed; S4, degassing preheating: when the vacuum degree in the Joule hot pressing furnace is less than 5x10 -3 Pa, the pre-pressure is reduced to 0.5-1.0 MPa, the temperature is started to be increased at a heating rate of 4-8 ℃ / min, when the temperature reaches 600 ℃, the temperature is kept for not less than 15 min, and the vacuum degree in the furnace reaches ≤1x10 -2 Pa, the degassing preheating is completed; S5, medium temperature transition: after heating at a rate of 8-12 °C / min to 1100 °C and holding for ≥5 min, the pressure is increased to 5 MPa, 10 MPa and 15 MPa at 900 °C, 1000 °C and 1100 °C respectively in three steps, and the vacuum degree in the furnace is ≤5x10 -2 Pa after the medium temperature transition is completed; S6, high-temperature sintering: after being heated at a heating rate of 8-12 ℃ / min to 1130-1200 ℃, the pressure is increased to 25-30 MPa, and after being kept for 8-20 min, the high-temperature sintering process is completed; S7, slow cooling: the pressure is reduced to 0-5 MPa, the cooling rate is 3-5 ℃ / min, high-purity argon is filled at a flow rate of 2-3 L / min and is pressurized to 50-80 kPa in steps, then the gas filling is stopped, the temperature is reduced to 1000-950 ℃, and then the pressure is completely released, and the slow cooling is completed; S8, furnace cooling: when the temperature is reduced to 800 ℃, the cooling rate is ≤10 ℃ / min, and when the temperature is reduced to 300 ℃, the furnace cooling is completed to below 100 ℃; S9, discharging: the graphite mold is taken out after being deflated, the product is pressed out, the surface graphite is ground off, and the preparation of the magnesium fluoride target material is completed.

2. The method of producing a magnesium fluoride ceramic sputtering target according to claim 1, characterized by: In step S1, the ultimate vacuum degree of the vacuum drying furnace is ≤6.5x10 -2 Pa.

3. The method of producing a magnesium fluoride ceramic sputtering target according to claim 1, characterized by: In step S2, the graphite mold uses an isotropic fine-grained isostatic pressing graphite mold with a compressive strength exceeding 150 MPa; the graphite mold has an electrical conductivity higher than 1.5 x 10 4 S / m, a thermal conductivity higher than 120 W / (m K), and an ash content ≤ 200 ppm.

4. The method of producing a magnesium fluoride ceramic sputtering target according to claim 1, characterized by: In step S2, the ratio of the wall thickness of the concave mold to the inner diameter is 0.4-0.6, the ratio of the height of the concave mold to the height of the target material is 5-16, and the inner diameter of the concave mold is 2.0%-3.5% larger than the designed diameter of the target material; the outer diameter of the convex mold is 1.4%-3.2% larger than the designed diameter of the target material.

5. The method of claim 1, wherein the method further comprises: In step S3, the thickness of the molybdenum and tantalum foil is 0.15-0.5 mm. ​ 6. The method of producing a magnesium fluoride ceramic sputtering target according to claim 1, characterized by: In step S3, the thickness of the graphite paper is 0.1-0.2 mm, the carbon content is higher than 99%, the tensile strength is ≥4.0 MPa, the sulfur content is ≤300 ppm, and the chlorine content is ≤35 ppm.

7. The method of producing a magnesium fluoride ceramic sputtering target according to claim 1, characterized by: In step S3, the BN coating is obtained by brushing, spraying or chemical vapor deposition after mixing BN powder with alcohol, the content of BN is not less than 99.0%, the content of B2O3 is not higher than 0.5%, and the thickness of the coating is 30-60 μm.

8. The method of producing a magnesium fluoride ceramic sputtering target according to claim 1, characterized by: In step S3, the asbestos felt is a high-temperature asbestos felt with a thickness of ≥7 mm, the surface area of the unfolded asbestos felt is larger than the outer surface area of the graphite mold, and the width of the asbestos felt is 3-7 mm higher than the axial height of the graphite mold.

9. The method of producing a magnesium fluoride ceramic sputtering target according to claim 1, characterized by: In step S9, after discharging, the product is detected, the chemical composition, the density and the hardness of the product are measured, and the product is packaged and stored after being analyzed to be qualified.

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