Preparation method of iridium sputtering target with low loss rate and iridium sputtering target

Abstract

The present application belongs to the technical field of noble metal sputtering target material, and particularly relates to a preparation method of iridium sputtering target material with low loss rate and the iridium sputtering target material. The present application adopts a vacuum high-frequency induction heating furnace to smelt iridium sheets, and the gas in the cavity is extracted before smelting starts, and protective gas is filled to keep the pressure at 7x10 4 Pa-9x10 4 Pa at all times, so as to avoid oxidation of the melt by directly contacting air, and reduce the burning loss of the melt by filling protective gas. The present application performs heat treatment on the cast ingot obtained by directional solidification, strictly controls the surface temperature of the cast ingot to be less than 1450 DEG C, controls the surface activity of the cast ingot, ensures that oxidation is not easy to occur, continuously fills protective gas to cover the surface of the cast ingot during the rolling process, reduces the contact of the surface of the cast ingot with oxygen and nitrogen, and further controls the thickness of the reaction layer of the final product, reduces the machining turning amount, and further controls the loss rate to be less than 1 ‰.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of precious metal sputtering targets, and particularly relates to a preparation method of an iridium sputtering target with low loss rate and the iridium sputtering target. BACKGROUND

[0002] Iridium (Ir) is a platinum group metal with a face-centered cubic structure, and has a melting point as high as 2443℃, which is the highest among all precious metals. Iridium has a high density (22.65 g / cm 3 ), stable chemical properties, high hardness, and good high-temperature performance, and is one of the metals with the best thermal strength and thermal stability at high temperatures, and is also a metal with a very high melting point and strong oxidation resistance. In addition, it is also one of the most corrosion-resistant metals, and can withstand the corrosion of many molten reagents and high-temperature silicates, and can resist the corrosion of almost all acids, aqua regia, molten metals, and even silicates at high temperatures.

[0003] Due to excellent physical and chemical stability, iridium thin films are increasingly widely used in the field of electronic information industry. For example, in a micro-electro-mechanical system (MEMS), pure iridium thin films are used as upper electrode layers (for leading electrodes) and lower electrode layers (for connecting substrate layers), and Ir-Ta-O composite thin films are used as electrode layers of ferroelectric capacitors in integrated circuits; the pure iridium thin films are directly obtained by using iridium sputtering targets as source materials and performing magnetron sputtering in an argon atmosphere; and the Ir-Ta-O composite thin films are obtained by using iridium targets and tantalum targets and performing reactive co-sputtering in an oxygen atmosphere.

[0004] The iridium sputtering target is a raw material for preparing an iridium thin film, and the iridium sputtering target is prepared from iridium metal. The iridium metal has a high melting point, and the loss is high when a traditional process is used, because oxidation slag is generated on the surface of the ingot after melting, the oxidation slag expands during hot rolling, and the oxidation slag falls off under the action of stress and strain, which causes the loss of part of the iridium metal, so that the loss rate during preparation is often higher than 2‰. High loss not only makes the production cost of the iridium sputtering target high, but also causes resource waste. SUMMARY

[0005] In view of the problems in the prior art, the preparation process of the iridium sputtering target is improved from the perspective of reducing the production cost of the iridium sputtering target, so that the loss rate of iridium during the preparation of the iridium target is less than 1‰, and the performance of the iridium sputtering target is ensured. The application provides a preparation method of an iridium sputtering target with low loss rate and the iridium sputtering target, and specifically includes the following contents.

[0006] The preparation method of the iridium sputtering target with low loss rate includes the following steps:

[0007] (1) Melting: iridium pieces with a purity of not less than 4N are added into a vacuum high-frequency induction heating furnace, the iridium pieces are tightly laid along the melting crucible, and vacuum is first extracted to 9x10-4 Pa-9×10 -3 Pa, protective gas is filled to the vacuum degree of 7×10 4 Pa-9×10 4 Pa, smelting is carried out at the temperature of 2500-2700℃, and the iridium melt is obtained; compared with the prior art using the vacuum medium-frequency induction heating furnace, the vacuum high-frequency induction heating furnace is used for smelting the iridium sheet in the present patent, and the vacuum high-frequency induction heating furnace has the advantages of lower cost, smaller floor area, faster heating rate, smaller single smelting feeding amount and the like, the gas in the cavity is extracted before smelting starts, and the protective gas is filled to keep the vacuum degree of 7×10 4 Pa-9×10 4 Pa, so that the melt can be effectively prevented from being directly contacted with air to be oxidized and the melt burning loss is reduced.

[0008] (2) Refining: the vacuum high-frequency induction heating furnace is used for continuously heating the iridium melt, and the melt temperature is kept at 2600-2700℃, and the electromagnetic stirring is started; the method disclosed in the present application strictly controls the range of the melt temperature, so that the oxidation is reduced and the loss of raw materials is reduced under the condition of ensuring sufficient melting.

[0009] (3) Directional solidification: the water-cooled mold with the cooling water connected to the bottom is used for casting the iridium melt, and the casting process is as follows: first, the melt is cast at the rate of 5-8cm 3 / s to 1 / 5-1 / 3 of the water-cooled mold; then, the casting rate is slowed down to 3-5cm 3 / s, and the melt is cast to 2 / 5-3 / 5 of the water-cooled mold; and then, the melt is slowly cast at the rate of 1-2cm 3 / s, and after the casting is completed and cooled, the ingot is obtained; first, the melt is cast into the water-cooled mold at the rate of 5-8cm 3 / s, and the melt is quickly poured to give the melt a large momentum, so that the high-temperature melt first quickly grows along the inside of the wall of the water-cooled mold, and therefore the melt with large momentum can impact the crystallization zone to form broken grains flowing back to the inside of the melt, and the subsequent nucleation center is increased to ensure that the ingot has a certain number of fine grains. Then, the melt is cast into the water-cooled mold at the rate of 3-5cm 3 / s, and the casting rate is reduced to ensure that the columnar crystals grown subsequently are not broken. Finally, the melt is cast into the water-cooled mold at the rate of 1-2cm 3 / s, and the slow feeding is completed to reduce the depth of the riser.

[0010] (4) Slitting: the iridium ingot is slitted to obtain the iridium target blank;

[0011] (5) Rolling: the cut iridium target blank is put into an atmosphere heat treatment furnace, a reducing atmosphere is passed in, heated to 1100-1450℃, and kept for 0.5-2h; then 3-6 passes of rolling is carried out, a protective gas is continuously passed in to cover the surface of the iridium target blank during the rolling process, and a high-density high-oriented iridium target semi-finished product is obtained after the rolling is completed; the directional solidification and cut iridium target blank is subjected to heat treatment, the surface temperature is strictly controlled to be less than 1450℃, the surface activity of the ingot can be effectively controlled, oxidation is not prone to occur, a protective gas is continuously passed in to cover the surface of the ingot during the rolling process, the surface of the ingot is reduced to contact with oxygen and nitrogen, and then the thickness of the reaction layer of the final product is controlled, the machining turning amount is reduced, and then the loss rate is controlled to be less than 1‰, compared with the traditional production of iridium sputtering target material using a vacuum medium-frequency induction heating furnace, the production cost of the iridium sputtering target material can be reduced by 10-20%, and the price of the iridium sputtering target material is greatly reduced.

[0012] (6) Reduction: the iridium target semi-finished product is put into an atmosphere heat treatment furnace, a reducing atmosphere is passed in, heated to 300-600℃, kept for 0.5-1h, and taken out after furnace cooling;

[0013] (7) Machining: the reduced iridium target semi-finished product is machined to obtain the iridium sputtering target material, and the mass loss rate of the iridium sputtering target material is less than 1‰ compared with the iridium sheet in step (1).

[0014] Preferably, the protective gas in step (1) is one or more of helium, argon and xenon with a purity higher than 4N.

[0015] Preferably, the time of the electromagnetic stirring in step (2) is 5-15min.

[0016] Preferably, the material of the water-cooled mold in step (3) is one of zirconia, high-purity iridium, copper and aluminum oxide with a purity higher than 4N.

[0017] Preferably, the reducing atmosphere in step (6) is one or a mixture of hydrogen and carbon monoxide.

[0018] Preferably, the rolling in step (5) strictly controls the pass reduction of each rolling to be 3-8%, and the iridium target blank is rotated by 80°-100° after each rolling before the next rolling.

[0019] An iridium sputtering target material prepared by the method of the present application, the target surface of the iridium sputtering target material presents (111) crystal face preferred orientation, the density is not less than 99.8%, the grain size is less than 300μm, there is no internal defect, and the purity is not less than 4N.

[0020] The present application has the following beneficial effects:

[0021] (1) Compared with the vacuum medium frequency induction heating furnace, the vacuum high frequency induction heating furnace is used for iridium sheet smelting in the application, and the vacuum high frequency induction heating furnace has the advantages of lower cost, smaller floor area, faster heating rate, smaller single smelting feeding amount and the like, the gas in the cavity is extracted before smelting starts, and the protective gas is filled to keep the pressure at 7*10 4 Pa-9*10 4 Pa, so as to avoid direct contact of the melt with air to cause oxidation, and the filling of the protective gas reduces the burning loss of the melt.

[0022] (2) The ingot obtained by directional solidification is subjected to heat treatment, the surface temperature of the ingot is strictly controlled to be less than 1450 DEG C, the surface activity of the ingot is controlled, oxidation is not easy to occur, the protective gas is continuously introduced to cover the surface of the ingot during rolling, the surface of the ingot is reduced to contact with oxygen and nitrogen, and then the thickness of the reaction layer of the final product is controlled, the machining turning amount is reduced, and then the loss rate is controlled to be less than 1 ‰, compared with the traditional vacuum medium frequency induction heating furnace for producing iridium sputtering target material, the cost of the iridium sputtering target material produced by the application can be reduced by 10-20 %, and the price of the iridium sputtering target material is greatly reduced.

[0023] (3) The iridium sputtering target material prepared by the method has a face-centered cubic structure, and the (111) crystal surface is a close-packed surface with weak binding force, which can effectively improve the sputtering rate under rated power, and the target surface of the iridium sputtering target material is realized by directional solidification and rolling technology. Preferential orientation of (111) crystal surface, the application finally realizes the reduction of the production cost of iridium sputtering target material while ensuring the performance of iridium sputtering target material. BRIEF DESCRIPTION OF DRAWINGS

[0024] Figure 1 The physical map of the iridium sputtering target material prepared by the application;

[0025] Figure 2 The metallographic map of the iridium sputtering target material prepared by the application. DETAILED DESCRIPTION

[0026] The application will be described in detail below in combination with the drawings and specific embodiments. The embodiments shown below do not limit the invention content recited in the claims in any way. In addition, the entire content of the constitution represented by the following embodiments is not limited to the solution necessary for the invention recited in the claims.

[0027] A low-loss-rate iridium sputtering target material preparation method, the target surface of the iridium sputtering target material presents (111) crystal surface preferential orientation, the density is not less than 99.8 %, the grain size is less than 300 μm, there is no internal defect, the purity is not less than 4N, and the method comprises the following steps:

[0028] (1) Melting: Add iridium sheets with a purity of not less than 4N into a vacuum high-frequency induction heating furnace. Spread the iridium sheets tightly along the melting crucible. First, evacuate to 9×10 -4 -9×10 -3 Pa (e.g. 9.5×10 -4 Pa, 1×10 -3 Pa, 3×10 -3 Pa, 5×10 - 3 Pa, 7×10 -3 Pa, etc.), and then fill with protective gas to a vacuum degree of 7×10 4 Pa-9×10 4 Pa (e.g. 7.2×10 4 Pa, 7.5×10 4 Pa, 8×10 4 Pa, 8.5×10 4 Pa, etc.), smelting at a temperature of 2500-2700° C. (e.g., 2520° C., 2550° C., 2580° C., 2600° C., 2620° C., 2650° C., 2680° C., etc.) to obtain an iridium melt; the protective gas is one or more of helium, argon, and xenon with a purity higher than 4N;

[0029] (2) Refining: The iridium melt is continuously heated in a vacuum high-frequency induction heating furnace, and the melt temperature is maintained at 2600-2700°C (e.g., 2620°C, 2640°C, 2660°C, 2680°C, etc.), and electromagnetic stirring is turned on for 5-15 minutes (e.g., 6 minutes, 8 minutes, 10 minutes, 12 minutes, 14 minutes, etc.);

[0030] (3) Directional solidification: Use a water-cooled mold with cooling water at the bottom to cast the iridium melt. The casting process is: first, 5-8 cm 3 / s (e.g. 5.2cm 3 / s, 5.5cm 3 / s, 6.0cm 3 / s、6.5cm 3 / s、7.0cm 3 / s、7.5cm 3 / s, etc.) to 1 / 5-1 / 3 of the water-cooled mold; then slow down the casting speed to 3-5cm 3 / s (e.g. 3.2cm 3 / s, 3.5cm 3 / s, 3.8cm 3 / s, 4.0cm 3 / s, 4.2cm 3 / s, 4.5cm 3 / s、4.8cm3 / s, etc.), cast to 2 / 5-3 / 5 of the water-cooled mold; then 1-2cm 3 / s (e.g. 1.2cm 3 / s, 1.4cm 3 / s, 1.5cm 3 / s, 1.6cm 3 / s, 1.8cm 3 / s, 1.9cm 3 / s, etc.) to slowly cast, and after the casting is completed and cooled, an ingot is obtained; when the casting is first started, the ingot is cast at a rate of 5-8cm 3 / s is poured into the water-cooled mold. The rapid pouring gives the melt a large momentum. When the high-temperature melt contacts the inner wall of the water-cooled mold, it first grows rapidly along the internal crystallization. Therefore, the melt with a large momentum can impact the crystallization area, forming broken grains that flow back into the melt, subsequently increasing the nucleation center to ensure that the ingot has a certain number of fine grains. Then, at 3-5cm 3 / s is poured into the water-cooled mold, reducing the casting speed to ensure that the subsequent growth of columnar crystals will not be broken. 3 / s is poured into the water-cooled mold, and the shrinkage is slowly completed to reduce the riser depth. The material of the water-cooled mold is one of zirconium dioxide with a purity higher than 4N, high-purity iridium, copper, and aluminum oxide;

[0031] (4) Cutting: Cutting the iridium ingot to obtain an iridium target blank;

[0032] (5) Rolling: Place the cut iridium target blank into an atmosphere heat treatment furnace, introduce a reducing atmosphere, heat to 1100-1450°C (for example, 1150°C, 1200°C, 1250°C, 1300°C, 1350°C, 1400°C, etc.), and keep warm for 0.5-2h (for example, 0.6h, 0.8h, 1.0h, 1.2h, 1.5h, 1.8h, etc.); then perform 3-6 passes of rolling, strictly control the pass reduction of each rolling to 3-8%, rotate the iridium target blank 80°-100° after each rolling, and then perform the next rolling. During the rolling process, a protective gas is continuously introduced to cover the surface of the iridium target blank. After the rolling is completed, a highly dense and highly oriented iridium target semi-finished product is obtained;

[0033] (6) Reduction: Place the iridium target semi-finished product into an atmosphere heat treatment furnace, introduce a reducing atmosphere, heat to 300-600°C (e.g., 350°C, 400°C, 450°C, 500°C, 550°C, etc.), keep warm for 0.5-1h (e.g., 0.6h, 0.7h, 0.8h, 0.9h, etc.), cool with the furnace and then take it out; the reducing atmosphere is one of hydrogen and carbon monoxide atmospheres or a mixture of the two;

[0034] (7) Machining: machining the reduced iridium target semi-finished product to obtain the iridium sputtering target, the mass loss rate of the iridium sputtering target is <1 ‰ compared with the mass of the iridium sheet in step (1).

[0035] Example 1

[0036] A method for preparing an iridium sputtering target with low loss rate, the specific preparation steps are as follows:

[0037] (1) Melting: 500 g of iridium sheet with a purity of not less than 4N is sequentially placed in a vacuum high-frequency induction heating furnace melting furnace, the iridium plate is laid tightly along the melting crucible, the vacuum degree in the furnace is reduced to 9 × 10 -4 Pa, the vacuum valve is closed, and a protective gas is filled to maintain the vacuum degree in the furnace at 8 × 10 4 Pa, the vacuum high-frequency induction heating furnace is started, the heating system is turned on, and the temperature is quickly raised to 2600℃;

[0038] (2) Refining: the induction coil of the vacuum high-frequency induction heating furnace continuously heats the molten melt after melting, keeps the melt temperature at 2650℃, and starts electromagnetic stirring for 8 minutes;

[0039] (3) Directional solidification: the iridium melt is cast using a water-cooled mold with cooling water connected at the bottom, the casting process is as follows: first cast at a rate of 5 cm 3 / s to 1 / 4 of the water-cooled mold; then slow down the casting speed to 3 cm 3 / s, cast to 1 / 2 of the water-cooled mold; then slowly cast at a rate of 1 cm 3 / s, after the casting is completed and cooled, a cast ingot is obtained;

[0040] (4) Slitting: the cast ingot is slitted to obtain a target blank;

[0041] (5) Rolling: the slitted target blank is placed in an atmosphere heat treatment furnace, a reducing atmosphere is introduced, heated to 1250℃, and held for 1 hour, 4 passes of rolling are carried out, the pass reduction amount is strictly controlled at 4%, the target blank is rotated by 90° after each rolling, and a protective gas is continuously introduced to cover the surface of the target blank during the rolling process, obtaining a high-density high-orientation iridium semi-finished product;

[0042] (6) Reduction: the semi-finished product is placed in an atmosphere heat treatment furnace, a reducing atmosphere is introduced, heated to 400℃, and held for 0.6 hours, and the iridium semi-finished product is taken out after furnace cooling;

[0043] (7) Machining: machining the iridium semi-finished product to obtain an iridium target according to needs, and recycling the iridium scraps generated by machining.

[0044] The actual picture of the iridium sputtering target finally prepared in this example is shown in Figure 1. Figure 1The density of the iridium sputtering target was tested by drainage method, and the relative density of the target was 99.98%. The grain of the iridium sputtering target was analyzed, and the metallographic image is shown in FIG. 2. As shown in FIG. 2, the grain size of the iridium sputtering target was uniform, and the grain size was within 300 μm. Finally, the weight of the iridium sputtering target was 499.73 g, the loss rate was 0.054%, and the purity met the 4N requirement after GDMS test. Figure 2 The grain size of the iridium sputtering target was uniform, and the grain size was within 300 μm. Finally, the weight of the iridium sputtering target was 499.73 g, the loss rate was 0.054%, and the purity met the 4N requirement after GDMS test.

[0045] Example 2

[0046] A method for preparing an iridium sputtering target with low loss rate, and the specific preparation steps are as follows:

[0047] (1) Melting: 240 g of iridium sheet with a purity of not less than 4N was sequentially placed in a vacuum high-frequency induction heating furnace melting furnace, and the iridium plate was tightly laid along the melting crucible. The vacuum degree in the furnace was reduced to 9 × 10 -4 Pa, the vacuum valve was closed, and the protective gas was filled to maintain the vacuum degree in the furnace at 9 × 10 4 Pa. The vacuum high-frequency induction heating furnace was started, and the heating system was turned on to quickly raise the temperature to 2500℃.

[0048] (2) Refining: The induction coil of the vacuum high-frequency induction heating furnace continuously heated the molten melt after melting, maintained the melt temperature at 2650℃, and turned on the electromagnetic stirring for 8 minutes.

[0049] (3) Directional solidification: The iridium melt was cast using a water-cooled mold with cooling water connected to the bottom. The casting process was as follows: first, cast at a rate of 8 cm 3 / s to 1 / 4 of the water-cooled mold; then slow down the casting speed to 5 cm 3 / s to 1 / 2 of the water-cooled mold; then slowly cast at a rate of 2 cm 3 / s, and after the casting was completed and cooled, a cast ingot was obtained.

[0050] (4) Cutting: The cast ingot was cut to obtain a target blank.

[0051] (5) Rolling: The cut target blank was placed in an atmosphere heat treatment furnace, a reducing atmosphere was introduced, heated to 1250℃, and held for 0.5 hours. Three passes of rolling were performed, with the pass reduction strictly controlled at 3%. After each pass of rolling, the target blank was rotated by 90°. Protective gas was continuously introduced to cover the surface of the target blank during the rolling process, and a high-density high-orientation iridium semi-finished product was obtained.

[0052] (6) Reduction: The semi-finished product was placed in an atmosphere heat treatment furnace, a reducing atmosphere was introduced, heated to 400℃, and held for 0.6 hours. After cooling in the furnace, the iridium semi-finished product was taken out.

[0053] (7) Machining: machining the iridium semi-finished product as needed to obtain an iridium target, and recycling the iridium scraps generated in the machining.

[0054] The final iridium sputtering target prepared in this embodiment was tested by the drainage method, and the relative density of the target was 99.98%. Sampling analysis of the grain size of the iridium sputtering target showed that the grain size of the iridium sputtering target was uniform, and the grain size was within 300 μm. Finally, an iridium sputtering target with a weight of 239.82 g and a loss rate of 0.075% was obtained, and the purity met the 4N requirement after GDMS testing.

[0055] Example 3

[0056] A method for preparing an iridium sputtering target with low loss rate, comprising the following steps:

[0057] (1) Melting: iridium pieces with a purity of not less than 4N were added into a vacuum high-frequency induction heating furnace, the iridium pieces were laid flat and closely along the melting crucible, vacuum was first extracted to 7 x 10 -4 Pa, then protective gas was filled to a vacuum degree of 8 x 10 4 Pa, and the iridium was melted at a temperature of 2500°C to obtain an iridium melt; the protective gas was helium gas with a purity higher than 4N;

[0058] (2) Refining: the vacuum high-frequency induction heating furnace was continuously heated to keep the temperature of the iridium melt at 2600°C, and electromagnetic stirring was started, and the stirring time was 5 min;

[0059] (3) Directional solidification: the iridium melt was cast using a water-cooled mold with cooling water connected to the bottom, and the casting process was as follows: first, the casting rate was 6 cm 3 / s, and the iridium melt was cast to 1 / 5 of the water-cooled mold; then the casting rate was slowed down to 3.5 cm 3 / s, and the iridium melt was cast to 2 / 5 of the water-cooled mold; then the casting rate was slowed down to 1.2 cm 3 / s, and the iridium melt was slowly cast until the casting was completed and the ingot was cooled; the material of the water-cooled mold was zirconia with a purity higher than 4N;

[0060] (4) Slitting: the iridium ingot was slitted to obtain an iridium target blank;

[0061] (5) Rolling: the slitted iridium target blank was placed into an atmosphere heat treatment furnace, a reducing atmosphere was introduced, and the temperature was raised to 1100°C and kept for 0.5 h; then 3 passes of rolling were performed, and the pass reduction amount of each pass was strictly controlled to be 3%, and the iridium target blank was rotated by 88° after each pass of rolling before the next pass of rolling; a protective gas was continuously introduced to cover the surface of the iridium target blank during the rolling process; and a high-density and high-orientation iridium target semi-finished product was obtained after the rolling was completed;

[0062] (6) Reduction: Put the iridium target material semi-finished product into an atmosphere heat treatment furnace, pass a reducing atmosphere, heat to 300°C, keep for 0.5h, take out after furnace cooling; the reducing atmosphere is one or a mixture of both of hydrogen gas and carbon monoxide gas atmosphere;

[0063] (7) Machining: Machining the reduced iridium target material semi-finished product to obtain the iridium sputtering target.

[0064] The final iridium sputtering target prepared in this embodiment is tested by the drainage method, and the relative density of the target is ≥99.82%. Sampling analysis of the grain size of the iridium sputtering target shows that the grain size of the iridium sputtering target is uniform, the grain size is within 300μm, and the loss rate is 0.55‰, and the purity meets the 4N requirement after GDMS test.

[0065] Example 4

[0066] A method for preparing an iridium sputtering target with low loss rate, comprising the following steps:

[0067] (1) Melting: Put iridium pieces with a purity of not less than 4N into a vacuum high-frequency induction heating furnace, lay the iridium pieces closely along the melting crucible, first vacuumize to 9×10 -3 Pa, then fill in a protective gas to a vacuum degree of 9×10 4 Pa, and melt at a temperature of 2700°C to obtain an iridium melt; the protective gas is argon with a purity higher than 4N;

[0068] (2) Refining: continuously heat the iridium melt using a vacuum high-frequency induction heating furnace, keep the melt temperature at 2700°C, and start electromagnetic stirring, and the stirring time is 15min;

[0069] (3) Directional solidification: use a water-cooled mold with cooling water connected to the bottom to cast the iridium melt, and the casting process is as follows: first cast at a rate of 7cm 3 / s to 1 / 3 of the water-cooled mold; then slow down the casting speed to 4cm 3 / s, and cast to 3 / 5 of the water-cooled mold; then slowly cast at a rate of 1.5cm 3 / s, and after the casting is completed and cooled, an ingot is obtained; the material of the water-cooled mold is high-purity iridium with a purity higher than 4N;

[0070] (4) Slitting: slit the iridium ingot to obtain an iridium target blank;

[0071] (5) Rolling: the slit iridium target blank is placed in an atmosphere heat treatment furnace, a reducing atmosphere is introduced, heated to 1450℃, and held for 2h; then 6 passes of rolling are performed, and the pass reduction amount of each pass is strictly controlled to be 8%, and after each rolling, the iridium target blank is rotated by 98° before the next rolling, and a protective gas is continuously introduced to cover the surface of the iridium target blank during the rolling process, and a high-density and high-orientation iridium target material semi-finished product is obtained after the rolling is completed;

[0072] (6) Reduction: the iridium target material semi-finished product is placed in an atmosphere heat treatment furnace, a reducing atmosphere is introduced, heated to 600℃, and held for 1h, and then taken out after furnace cooling; the reducing atmosphere is carbon monoxide;

[0073] (7) Machining: the reduced iridium target material semi-finished product is machined to obtain the iridium sputtering target material.

[0074] The iridium sputtering target material finally prepared in this embodiment is tested by the drainage method, and the relative density of the target material is ≥99.95%. Sampling analysis of the grain size of the iridium sputtering target material shows that the grain size of the iridium sputtering target material is uniform, the grain size is within 300μm, the loss rate is 0.87‰, and the purity meets the 4N requirement after GDMS testing.

[0075] Example 5

[0076] A method for preparing an iridium sputtering target material with low loss rate, comprising the following steps:

[0077] (1) Melting: iridium pieces with a purity of not less than 4N are placed in a vacuum high-frequency induction heating furnace, and the iridium pieces are tightly laid along the melting crucible. First, vacuumize to 2×10 -3 Pa, then fill in a protective gas to a vacuum degree of 7.5×10 4 Pa, and melt at a temperature of 2550℃ to obtain an iridium melt; the protective gas is xenon gas with a purity higher than 4N;

[0078] (2) Refining: the vacuum high-frequency induction heating furnace is continuously heated to maintain the temperature of the iridium melt at 2620℃, and electromagnetic stirring is started, and the stirring time is 6min;

[0079] (3) Directional solidification: the iridium melt is cast using a water-cooled mold with cooling water connected to the bottom, and the casting process is as follows: first, cast at a rate of 7.5cm 3 / s to 1 / 4 of the water-cooled mold; then slow down the casting speed to 4.5cm 3 / s to 1 / 2 of the water-cooled mold; then slowly cast at a rate of 1.5cm 3 / s, and after the casting is completed and cooled, a cast ingot is obtained; the material of the water-cooled mold is copper with a purity higher than 4N;

[0080] (4) slitting: the iridium ingot is slitted to obtain an iridium target blank;

[0081] (5) rolling: the slitted iridium target blank is placed into an atmosphere heat treatment furnace, a reducing atmosphere is introduced, and heating is performed to 1150℃ for 1h; then 4 passes of rolling are performed, and the pass reduction amount of each pass is strictly controlled to be 4%, and the iridium target blank is rotated by 90° after each pass of rolling before the next pass of rolling; a protective gas is continuously introduced to cover the surface of the iridium target blank during rolling; and a high-density and high-orientation iridium target semi-finished product is obtained after rolling;

[0082] (6) reduction: the iridium target semi-finished product is placed into an atmosphere heat treatment furnace, a reducing atmosphere is introduced, and heating is performed to 400℃ for 0.6h, and the furnace is cooled down before the product is taken out; the reducing atmosphere is a mixture of hydrogen and carbon monoxide;

[0083] (7) machining: the reduced iridium target semi-finished product is machined to obtain the iridium sputtering target.

[0084] The iridium sputtering target prepared in this embodiment is tested by the drainage method, and the relative density of the target is ≥99.93%. The grains of the iridium sputtering target are sampled and analyzed, and it is observed that the grain size of the iridium sputtering target is uniform, the grain size is within 300μm, the loss rate is 0.51‰, and the purity meets the 4N requirement after GDMS testing.

[0085] Example 6

[0086] A method for preparing an iridium sputtering target with low loss rate, comprising the following steps:

[0087] (1) melting: iridium pieces with a purity of not less than 4N are placed into a vacuum high-frequency induction heating furnace, the iridium pieces are tightly laid along the melting crucible, vacuum is first extracted to 5×10 -3 Pa, a protective gas is then introduced to a vacuum degree of 8.5×10 4 Pa, and melting is performed at a temperature of 2600℃ to obtain an iridium melt; the protective gas is a mixed gas of helium, argon and xenon with a purity of more than 4N

[0088] (2) refining: the iridium melt is continuously heated using a vacuum high-frequency induction heating furnace, the melt temperature is maintained at 2680℃, and electromagnetic stirring is started, and the stirring time is 12min;

[0089] (3) directional solidification: the iridium melt is cast using a water-cooled mold with cooling water connected to the bottom, and the casting process is as follows: first, the casting speed is 8cm 3 / s, and the melt is cast to 1 / 4 of the water-cooled mold; then, the casting speed is slowed down to 3.3cm 3 / s, and the melt is cast to 1 / 2 of the water-cooled mold; and then, the casting speed is further slowed down to 1.8cm 3casting, and after the casting is completed and cooled, a ingot is obtained; the material of the water-cooled mold is aluminum oxide with a purity higher than 4N;

[0090] (4) slitting: the iridium ingot is slitted to obtain an iridium target blank;

[0091] (5) rolling: the slitted iridium target blank is placed into an atmosphere heat treatment furnace, a reducing atmosphere is introduced, heated to 1400℃, and held for 1.5h; then 5 passes of rolling are performed, and the pass reduction amount of each rolling is strictly controlled to be 3-8%, the iridium target blank is rotated by 90° after each rolling, and the next rolling is performed, a protective gas is continuously introduced to cover the surface of the iridium target blank during the rolling, and a high-density and high-orientation iridium target material semi-finished product is obtained after the rolling;

[0092] (6) reduction: the iridium target material semi-finished product is placed into an atmosphere heat treatment furnace, a reducing atmosphere is introduced, heated to 500℃, and held for 0.8h, and then taken out after furnace cooling; the reducing atmosphere is one or a mixture of both of hydrogen and carbon monoxide;

[0093] (7) machining: the reduced iridium target material semi-finished product is machined to obtain the iridium sputtering target material.

[0094] The iridium sputtering target material prepared in the embodiment is tested by the drainage method, and the relative density of the target material is ≥99.95%. Sampling analysis of the grain of the iridium sputtering target material shows that the grain size of the iridium sputtering target material is uniform, the grain size is within 300μm, the loss rate is 0.61‰, and the purity meets the 4N requirement after GDMS testing.

[0095] Comparative Example 1

[0096] A method for preparing an iridium sputtering target material, and the specific preparation steps are as follows:

[0097] (1) melting: 240g of iridium sheet with a purity not less than 4N is sequentially placed into a vacuum high-frequency induction heating furnace melting furnace, the iridium plate is laid flat and closely along the melting crucible, the vacuum degree in the furnace is maintained at 9×10 -3 Pa-9×10 -4 Pa, the vacuum high-frequency induction heating furnace is started, the heating system is turned on, and the temperature is quickly raised to 2500℃;

[0098] (2) refining: the induction coil of the vacuum high-frequency induction heating furnace continuously heats the molten melt after melting, maintains the melt temperature at 2650℃, and starts electromagnetic stirring for 8 minutes;

[0099] (3) directional solidification: a water-cooled mold with a bottom connected to cooling water is used for casting the melt, and the casting speed is controlled according to the following steps: first, quickly cast to 1 / 4 of the water-cooled mold, then slow down the casting speed to cast to 1 / 2 of the water-cooled mold, and then slowly cast, and after cooling, an ingot is obtained;

[0100] (4) Slitting: The ingot is slitted to obtain a target blank;

[0101] (5) Rolling: The slitted target blank is placed into an atmosphere heat treatment furnace, a reducing atmosphere is introduced, heated to 1250°C, and held for 0.5 hours, 3 passes of rolling are performed, the pass reduction is strictly controlled at 3%, the target blank is rotated by 90° after each rolling, and a protective gas is continuously introduced to cover the surface of the target blank during rolling to obtain a high-density high-orientation iridium semi-finished product;

[0102] (6) Reduction: The semi-finished product is placed into an atmosphere heat treatment furnace, a reducing atmosphere is introduced, heated to 400°C, and held for 0.6 hours, and the iridium semi-finished product is taken out after furnace cooling;

[0103] (7) Machining: The iridium semi-finished product is machined as needed to obtain an iridium target, and the iridium scraps generated during machining are recycled.

[0104] The iridium sputtering target material finally prepared in the comparative example 1 is tested by the drainage method, the relative density of the target material is 99.96%, the iridium sputtering target material is sampled and analyzed, the grain size of the iridium sputtering target material is uniform, the grain size is within 300 μm, the final weight of the iridium sputtering target material is 237.15 g, the loss rate is 1.1875%, and the purity meets the 4N requirement after GDMS testing.

[0105] During the smelting process, the increase of pressure by not charging a protective gas will increase the volatilization speed of iridium, causing high loss and greatly increasing the production cost, therefore, a proper protective gas should be charged during the smelting process.

[0106] Comparative example 2

[0107] A method for preparing an iridium sputtering target material, the specific preparation steps are as follows:

[0108] (1) Smelting: 240 g of iridium sheet with a purity of not less than 4N is sequentially placed into a vacuum high-frequency induction heating furnace smelting furnace, the iridium plate is laid flat and closely along the smelting crucible, the vacuum degree in the furnace is reduced to 9 x 10 -4 Pa, the vacuum valve is closed, a protective gas is charged to maintain the vacuum degree in the furnace at 9 x 10 4 Pa, the vacuum high-frequency induction heating furnace is started, the heating system is turned on, and the temperature is quickly raised to 2500°C;

[0109] (2) Refining: The induction coil of the vacuum high-frequency induction heating furnace continuously heats the molten melt after melting, the melt temperature is maintained at 2650°C, and the electromagnetic stirring is turned on for 8 minutes;

[0110] (3) Directional solidification: water-cooled mold with bottom access to cooling water is used when casting the melt, and the casting speed is controlled to pour quickly to 1 / 4 of the water-cooled mold, slow down the casting speed to pour to 1 / 2 of the water-cooled mold, and start slow casting, and get the ingot after cooling;

[0111] (4) Slitting: the ingot is slitted to get the target blank;

[0112] (5) Rolling: the slitted target blank is put into a heat treatment furnace, heated to 1250℃, and kept for 0.5 hours, and 3 passes of rolling are performed, and the pass reduction is strictly controlled to be 3%, and the target blank is rotated by 90° after each rolling, and a high-density and high-orientation iridium semi-finished product is obtained;

[0113] (6) Reduction: the semi-finished product is put into an atmosphere heat treatment furnace, and a reducing atmosphere is introduced, and heated to 400℃, and kept for 0.6 hours, and the iridium semi-finished product is taken out after furnace cooling;

[0114] (7) Machining: the iridium semi-finished product is machined as needed to obtain an iridium target, and the iridium scraps generated by machining are recycled.

[0115] The iridium sputtering target material finally prepared in the comparative example 2 is tested by the drainage method, and the relative density of the target material is 99.97%. The grain of the iridium sputtering target material is analyzed, and it is observed that the grain size of the iridium sputtering target material is uniform, and the grain size is within 300μm. Finally, the weight of the iridium sputtering target material is 238.22g, the loss rate is 0.742%, and the purity meets the 4N requirement after GDMS test.

[0116] In the rolling process, the atmosphere heat treatment furnace is not used for heating, and the protective gas is not used to cover the surface of the target blank during the rolling process. The surface of the target blank will react during the heating process, and the surface oxide layer will separate due to the action of the stress field and the temperature field after rolling, and the loss rate increases.

[0117] Comparative Example 3

[0118] The difference between the comparative example and the example 1 is that the uniform casting rate in step (3) is 4.5cm 3 / s, and other conditions are the same.

[0119] The iridium sputtering target material finally prepared in the comparative example is tested by the drainage method, and the relative density of the target material is 99.36%, and the loss rate of the iridium sputtering target material is 4.1%.

[0120] Comparative Example 4

[0121] The difference between the comparative example and the example 2 is that the uniform casting rate in step (3) is 10cm 3 / s, and other conditions are the same.

[0122] The iridium sputtering target prepared in the present comparative example was tested by drainage method, and the relative density of the target was 99.01%, and the loss rate of the iridium sputtering target was 4.6%.

[0123] Comparative Example 5

[0124] The difference between the present comparative example and Example 3 is that the directional solidification casting process is as follows: first casting at a rate of 10 cm / s; then slowing down the casting speed to 8 cm / s; and then slowly casting at a rate of 1 cm / s. After the casting is completed and cooled, the ingot is obtained, and other conditions are the same. 3 3 3 The difference between the present comparative example and Example 3 is that the directional solidification casting process is as follows: first casting at a rate of 10 cm / s; then slowing down the casting speed to 8 cm / s; and then slowly casting at a rate of 1 cm / s. After the casting is completed and cooled, the ingot is obtained, and other conditions are the same.

[0125] The iridium sputtering target prepared in the present comparative example was tested by drainage method, and the relative density of the target was 99.01%, and the loss rate of the iridium sputtering target was 4.6%.

[0126] The above description of disclosed embodiments enables one of ordinary skill in the art to make or use the application. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the generic principles defined herein can be applied to other embodiments without departing from the spirit or scope of the application. Thus, the present application is not intended to be limited to the embodiments shown herein but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.​​

Claims

1. A method for preparing an iridium sputtering target with a low loss rate, characterized in that: The method comprises the following steps: (1) Melting: pure iridium pieces with purity not less than 4N were put into a vacuum high-frequency induction heating furnace, vacuum was first extracted to 9x10 -4 Pa, then protective gas was filled to vacuum degree of 7x10 -3 Pa, and then melted at temperature of 2500-2700 ℃ to obtain iridium melt. (2) Casting: the iridium melt was cast into a graphite mold to obtain an ingot with a size of 100 mmx100 mmx 10 mm. (3) Homogenizing annealing: the ingot was put into a vacuum high-frequency induction heating furnace, vacuum was first extracted to 9x10 4 Pa, then protective gas was filled to vacuum degree of 7x10 4 Pa, and then homogenizing annealed at temperature of 2000-2100 ℃ for 2-3 h. (4) Hot rolling: the ingot was hot rolled to a thickness (2) Refining: continuously heating the iridium melt by using a vacuum high-frequency induction heating furnace, keeping the melt temperature at 2600-2700℃, and starting electromagnetic stirring; (3) Directional solidification: iridium melt casting using a water-cooled mold with bottom access to cooling water, casting process: first cast at a rate of 5-8 cm / s to 1 / 5-1 / 3 of the water-cooled mold; then slow down the casting speed to 3-5 cm / s, cast to 2 / 5-3 / 5 of the water-cooled mold; then slowly cast at a rate of 1-2 cm / s, after casting is completed and cooled, get the ingot; 3 3 3 / s, cast to 2 / 5-3 / 5 of the water-cooled mold; then slowly cast at a rate of 1-2 cm / s, after casting is completed and cooled, get the ingot;​​ (4) Slitting: slitting the iridium ingot to obtain an iridium target blank; (5) Rolling: placing the slitted iridium target blank into an atmosphere heat treatment furnace, passing in a reducing atmosphere, heating to 1100-1450℃, and keeping the temperature for 0.5-2h; then performing 3-6 passes of rolling, continuously passing in a protective gas to cover the surface of the iridium target blank during the rolling process, and obtaining a high-density and high-oriented iridium target material semi-finished product after the rolling is completed; (6) Reduction: placing the iridium target material semi-finished product into an atmosphere heat treatment furnace, passing in a reducing atmosphere, heating to 300-600℃, keeping the temperature for 0.5-1h, taking out after furnace cooling; (7) Machining: machining the reduced iridium target material semi-finished product to obtain the iridium sputtering target material, and the mass loss rate of the iridium sputtering target material is less than 1‰ compared with the iridium sheet in step (1).

2. The method of claim 1, wherein the method further comprises the step of: The protective gas in steps (1) and (5) is one or more of helium, argon, and xenon with a purity higher than 4N. ​ 3. The method of claim 1, wherein the method further comprises the step of: The time of the electromagnetic stirring in step (2) is 5-15min. ​ 4. The method of claim 1, wherein the method further comprises the step of: The material of the water-cooled mold in step (3) is one of zirconia with a purity higher than 4N, high-purity iridium, copper, and aluminum oxide. ​ 5. The method of claim 1, wherein the method further comprises the step of: The reducing atmosphere in steps (5) and (6) is one or a mixture of both of hydrogen and carbon monoxide. ​ 6. The method of claim 1-5, wherein the method further comprises the step of: The rolling in step (5) strictly controls the pass reduction of each rolling to be 3-8%, and the iridium target blank is rotated by 80°-100° after each rolling before the next rolling.

7. An iridium sputter target produced by the method of any one of claims 1 to 6, characterized in that The target surface of the iridium sputtering target material presents (111) crystal plane preferred orientation, the density is not less than 99.8%, the grain size is less than 300μm, there is no internal defect, and the purity is not less than 4N.

Images