A cobalt-ruthenium target material and a method of manufacturing the same

Abstract

The application relates to the technical field of semiconductors, and discloses a cobalt-ruthenium target material and a preparation method thereof. A cobalt ingot with a purity of 2N8 (99.8%) and a ruthenium ingot with a purity of 3N (99.9%) are purified through vacuum distillation and arc melting to obtain high-purity 4N (99.99%) cobalt ingots and 4N (99.99%) ruthenium ingots. Then, a rotating hot rolling process is adopted to obtain a cobalt-ruthenium target material with uniform grain size and high grain orientation degree. The cobalt-ruthenium target material prepared by the traditional rolling process has problems such as uneven grain size and disordered grain orientation, and the application effectively improves the grain size uniformity and grain orientation degree of the target material. Moreover, the application has the advantages of simple preparation process, greatly reduced production cycle, reduced production cost and suitability for mass production.

Description

Technical Field

[0001] This invention relates to the field of semiconductor technology, specifically to a cobalt-ruthenium target and its preparation method. Background Technology

[0002] Cobalt, ruthenium, and other semiconductor sputtering targets are widely used in information storage, semiconductor chips, and other fields. They are produced using physical vapor deposition (PVD) technology, where high-pressure accelerated gaseous ions bombard the target, sputtering the target's atoms to form a thin film on a silicon wafer surface. In recent years, with the rapid development of the semiconductor industry, the demand for cobalt, ruthenium, and other sputtering targets has increased dramatically. The performance of semiconductor integrated circuit metal thin films mainly depends on the grain size and orientation of the target. Currently, the grain size and orientation of the target are mainly adjusted and controlled through processes such as homogenization treatment, thermomechanical processing, and recrystallization annealing.

[0003] Cobalt-based sputtering targets for semiconductors require a cobalt purity of 4N (99.99%) or higher. Typically, high-purity cobalt powder is first sintered into blocks, then high-purity cobalt ingots are obtained through a high-vacuum electron beam melting furnace. Finally, plastic deformation, annealing, and backplate welding are performed to obtain the finished product. However, targets prepared by traditional rolling processes often suffer from problems such as uneven grain size and disordered grain orientation. Therefore, it is of great significance to adopt new and efficient preparation methods to obtain high-purity cobalt and ruthenium, as well as cobalt-ruthenium targets with uniform grain size and high grain orientation. Summary of the Invention

[0004] The technical problem solved by this invention is to provide a cobalt-ruthenium target material and its preparation method, which solves the problems of uneven grain size and disordered grain orientation that occur in target materials prepared by traditional rolling processes. This invention uses a rotary hot rolling method to obtain cobalt-ruthenium target materials with uniform grain size and high grain orientation.

[0005] The technical solution of this invention is:

[0006] A method for preparing a cobalt-ruthenium target, the method comprising the following steps:

[0007] Step 1: The cobalt ingot with a purity of 2N8 (99.8%) is vacuum distilled once in a vacuum distillation furnace, then the cobalt ingot after the first distillation is vacuum distilled a second time, and finally the cobalt ingot is vacuum arc melted in an electric arc melting furnace to obtain high-purity 4N (99.99%) cobalt ingot.

[0008] Step 2: Vacuum distillation of 3N (99.9%) ruthenium ingots in a vacuum distillation furnace, followed by vacuum arc melting of the distilled ruthenium ingots in an electric arc melting furnace to obtain high-purity 4N (99.99%) ruthenium ingots.

[0009] Step 3: Take cobalt ingots and ruthenium ingots with a purity of 4N respectively, mix them and then perform vacuum melting to obtain cobalt-ruthenium alloy liquid. Pour the cobalt-ruthenium alloy liquid into a disc-shaped graphite mold to obtain high-purity cobalt-ruthenium alloy round ingots.

[0010] Step 4: The cobalt-ruthenium alloy round ingot obtained in Step 1 is subjected to multiple rotary hot rolling at a rotation angle of 120° for 2 to 3 cycles to obtain a cobalt-ruthenium alloy slab.

[0011] Step 5: Anneal the cobalt-ruthenium alloy slab to obtain a cobalt-ruthenium target.

[0012] Preferably, the temperature of the first distillation in step 1 is 1500–1550°C, and the vacuum degree is 1×10⁻⁶. -2 Pa; the secondary distillation temperature is 1550–1600℃, and the vacuum is 1×10⁻⁶. -2 Pa; the vacuum degree of electric arc melting is 1×10 -3 Pa.

[0013] Preferably, the distillation temperature in step 2 is 2600–2700°C, and the vacuum degree is 1×10⁻⁶. -3 Pa; the vacuum degree of electric arc melting is 1×10 -3 Pa.

[0014] Preferably, the atomic ratio of cobalt to ruthenium in step 3 is (50%–80%):(20%–50%).

[0015] Preferably, the vacuum melting temperature in step 3 is 1600–2000℃, the melting time is 2–4 hours, and the vacuum degree is 1×10⁻⁶. -3 Pa.

[0016] Preferably, in step 4, after each rolling pass, the rolling direction is rotated 120° for the next rolling pass, and each three rolling passes constitute one cycle, with a total rolling cycle of 2 to 3 cycles.

[0017] Preferably, in step 4, the total deformation of the hot-rolled cobalt-ruthenium alloy slab is 60% to 80%, the grain size is 120±20μm, and the proportion of grains with (0001) orientation is 40% to 60%.

[0018] Preferably, in step 4, the hot rolling temperature is 950–1350°C and the hot rolling time is 8–20 min.

[0019] Preferably, the annealing temperature in step 5 is 800–1000°C, and the annealing time is 2–4 hours.

[0020] The beneficial technical effects of this invention are:

[0021] This invention purifies cobalt ingots with a purity of 2N8 (99.8%) and ruthenium ingots with a purity of 3N (99.9%) through vacuum distillation and arc melting to obtain high-purity 4N (99.99%) cobalt ingots and 4N (99.99%) ruthenium ingots. Then, a rotary hot rolling process is used to obtain cobalt-ruthenium targets with uniform grain size and high grain orientation, overcoming the problems of uneven grain size and disordered grain orientation that occur in targets prepared by traditional rolling processes. This invention effectively improves the uniformity of grain size and grain orientation of the target material. Furthermore, it has the advantages of simple preparation process, significantly reduced production cycle, reduced production cost, and suitability for mass production. Detailed Implementation

[0022] The technical solution of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0023] Example 1

[0024] Step 1: Perform a single vacuum distillation of cobalt ingots with a purity of 2N8 (99.8%) in a vacuum distillation furnace at a temperature of 1500℃ and a vacuum degree of 1×10⁻⁶. -2 Pa; then the cobalt ingots after the first distillation are subjected to a second vacuum distillation at a temperature of 1600℃ and a vacuum of 1×10⁻⁶. -2 Pa; finally, the cobalt ingots were vacuum arc-melted in an electric arc furnace with a vacuum degree of 1×10⁻⁶. - 3 Pa yielded high-purity 4N (99.99%) cobalt ingots.

[0025] Step 2: Ruthenium ingots with a purity of 3N (99.9%) are vacuum distilled in a vacuum distillation furnace at a temperature of 2600℃ and a vacuum degree of 1×10⁻⁶. -3 Pa; then the distilled ruthenium ingot was vacuum arc-melted in an electric arc furnace at a vacuum degree of 1×10⁻⁶. -3 Pa yielded high-purity 4N (99.99%) ruthenium ingots.

[0026] Step 3: Take cobalt ingots and ruthenium ingots, both with a purity of 4N, mix them, and then vacuum melt them. Control the atomic ratio of cobalt to ruthenium to be 80%:20%, the vacuum melting temperature to be 1700℃, the melting time to be 4 hours, and the vacuum degree to be 1×10⁻⁶. -3 Pa, to obtain a cobalt-ruthenium alloy liquid, inject the cobalt-ruthenium alloy liquid into a disc-shaped graphite mold, and obtain a high-purity cobalt-ruthenium alloy ingot.

[0027] Step 4: The cobalt-ruthenium alloy round ingot obtained in Step 1 is subjected to multiple rotary hot rolling. After each rolling pass, the rolling direction is rotated 120° for the next rolling pass. Each rolling pass consists of three passes, and the rolling process lasts for two cycles. The hot rolling temperature is 1200℃, and the hot rolling time is 10 min to obtain a cobalt-ruthenium alloy slab. After hot rolling, the total deformation of the cobalt-ruthenium alloy slab is 62.4%, the grain size is 131 μm, and the proportion of grains with the (0001) plane orientation is 48.2%.

[0028] Step 5: Anneal the cobalt-ruthenium alloy slab at a temperature of 1000℃ for 2 hours to obtain a cobalt-ruthenium target.

[0029] Example 2

[0030] Step 1: Perform a single vacuum distillation of cobalt ingots with a purity of 2N8 (99.8%) in a vacuum distillation furnace at a temperature of 1550℃ and a vacuum degree of 1×10⁻⁶. -2 Pa; then the cobalt ingots after the first distillation are subjected to a second vacuum distillation at a temperature of 1600℃ and a vacuum of 1×10⁻⁶. -2 Pa; finally, the cobalt ingots were vacuum arc-melted in an electric arc furnace with a vacuum degree of 1×10⁻⁶. - 3 Pa yielded high-purity 4N (99.99%) cobalt ingots.

[0031] Step 2: Ruthenium ingots with a purity of 3N (99.9%) are vacuum distilled in a vacuum distillation furnace at a temperature of 2650℃ and a vacuum degree of 1×10⁻⁶. -3 Pa; then the distilled ruthenium ingot was vacuum arc-melted in an electric arc furnace at a vacuum degree of 1×10⁻⁶. -3 Pa yielded high-purity 4N (99.99%) ruthenium ingots.

[0032] Step 3: Take cobalt ingots and ruthenium ingots, both with a purity of 4N, mix them, and then vacuum melt them. Control the atomic ratio of cobalt to ruthenium to be 75%:25%, the vacuum melting temperature to be 1600℃, the melting time to be 4 hours, and the vacuum degree to be 1×10⁻⁶. -3 Pa, to obtain a cobalt-ruthenium alloy liquid, inject the cobalt-ruthenium alloy liquid into a disc-shaped graphite mold, and obtain a high-purity cobalt-ruthenium alloy ingot.

[0033] Step 4: The cobalt-ruthenium alloy round ingot obtained in Step 1 is subjected to multiple rotary hot rolling. After each rolling pass, the rolling direction is rotated 120° for the next rolling pass. Each rolling pass consists of three passes, and the rolling process is repeated for three cycles. The hot rolling temperature is 950℃, and the hot rolling time is 20 minutes to obtain a cobalt-ruthenium alloy slab. After hot rolling, the total deformation of the cobalt-ruthenium alloy slab is 72.6%, the grain size is 136μm, and the proportion of grains with the (0001) orientation is 41.4%.

[0034] Step 5: Anneal the cobalt-ruthenium alloy slab at a temperature of 1000℃ for 3 hours to obtain a cobalt-ruthenium target.

[0035] Example 3

[0036] Step 1: Perform a single vacuum distillation of cobalt ingots with a purity of 2N8 (99.8%) in a vacuum distillation furnace at a temperature of 1500℃ and a vacuum degree of 1×10⁻⁶. -2 Pa; then the cobalt ingots after the first distillation are subjected to a second vacuum distillation at a temperature of 1550℃ and a vacuum of 1×10⁻⁶. -2 Pa; finally, the cobalt ingots were vacuum arc-melted in an electric arc furnace with a vacuum degree of 1×10⁻⁶. - 3 Pa yielded high-purity 4N (99.99%) cobalt ingots.

[0037] Step 2: Ruthenium ingots with a purity of 3N (99.9%) are vacuum distilled in a vacuum distillation furnace at a temperature of 2700℃ and a vacuum degree of 1×10⁻⁶. -3 Pa; then the distilled ruthenium ingot was vacuum arc-melted in an electric arc furnace at a vacuum degree of 1×10⁻⁶. -3 Pa yielded high-purity 4N (99.99%) ruthenium ingots.

[0038] Step 3: Take cobalt ingots and ruthenium ingots, both with a purity of 4N, mix them, and then vacuum melt them. Control the atomic ratio of cobalt to ruthenium to be 65%:35%, the vacuum melting temperature to be 1800℃, the melting time to be 2 hours, and the vacuum degree to be 1×10⁻⁶. -3 Pa, to obtain a cobalt-ruthenium alloy liquid, inject the cobalt-ruthenium alloy liquid into a disc-shaped graphite mold, and obtain a high-purity cobalt-ruthenium alloy ingot.

[0039] Step 4: The cobalt-ruthenium alloy round ingot obtained in Step 1 is subjected to multiple rotary hot rolling. After each rolling pass, the rolling direction is rotated 120° for the next rolling pass. Each rolling pass consists of three passes, and the rolling process is repeated for three cycles. The hot rolling temperature is 1350℃, and the hot rolling time is 8 minutes to obtain a cobalt-ruthenium alloy slab. After hot rolling, the total deformation of the cobalt-ruthenium alloy slab is 62.3%, the grain size is 123μm, and the proportion of grains with the (0001) plane orientation is 57.9%.

[0040] Step 5: Anneal the cobalt-ruthenium alloy slab at a temperature of 800°C for 4 hours to obtain the cobalt-ruthenium target.

[0041] Example 4

[0042] Step 1: Perform a single vacuum distillation of cobalt ingots with a purity of 2N8 (99.8%) in a vacuum distillation furnace at a temperature of 1500℃ and a vacuum degree of 1×10⁻⁶.-2 Pa; then the cobalt ingots after the first distillation are subjected to a second vacuum distillation at a temperature of 1600℃ and a vacuum of 1×10⁻⁶. -2 Pa; finally, the cobalt ingots were vacuum arc-melted in an electric arc furnace with a vacuum degree of 1×10⁻⁶. - 3 Pa yielded high-purity 4N (99.99%) cobalt ingots.

[0043] Step 2: Ruthenium ingots with a purity of 3N (99.9%) are vacuum distilled in a vacuum distillation furnace at a temperature of 2600℃ and a vacuum degree of 1×10⁻⁶. -3 Pa; then the distilled ruthenium ingot was vacuum arc-melted in an electric arc furnace at a vacuum degree of 1×10⁻⁶. -3 Pa yielded high-purity 4N (99.99%) ruthenium ingots.

[0044] Step 3: Take cobalt ingots and ruthenium ingots, both with a purity of 4N, mix them, and then vacuum melt them. Control the atomic ratio of cobalt to ruthenium to be 55%:45%, the vacuum melting temperature to be 2000℃, the melting time to be 2 hours, and the vacuum degree to be 1×10⁻⁶. -3 Pa, to obtain a cobalt-ruthenium alloy liquid, inject the cobalt-ruthenium alloy liquid into a disc-shaped graphite mold, and obtain a high-purity cobalt-ruthenium alloy ingot.

[0045] Step 4: The cobalt-ruthenium alloy round ingot obtained in Step 1 is subjected to multiple rotary hot rolling. After each rolling pass, the rolling direction is rotated 120° for the next rolling pass. Each rolling pass consists of three passes, which is one revolution. The rolling process lasts for two revolutions. The hot rolling temperature is 1200℃ and the hot rolling time is 10min to obtain a cobalt-ruthenium alloy slab. After hot rolling, the total deformation of the cobalt-ruthenium alloy slab is 76.4%, the grain size is 131μm, and the proportion of grains with the (0001) plane orientation is 50.9%.

[0046] Step 5: Anneal the cobalt-ruthenium alloy slab at a temperature of 900°C for 3 hours to obtain a cobalt-ruthenium target.

[0047] Example 5

[0048] Step 1: Perform a single vacuum distillation of cobalt ingots with a purity of 2N8 (99.8%) in a vacuum distillation furnace at a temperature of 1500℃ and a vacuum degree of 1×10⁻⁶. -2 Pa; then the cobalt ingots after the first distillation are subjected to a second vacuum distillation at a temperature of 1600℃ and a vacuum of 1×10⁻⁶. -2 Pa; finally, the cobalt ingots were vacuum arc-melted in an electric arc furnace with a vacuum degree of 1×10⁻⁶. - 3 Pa yielded high-purity 4N (99.99%) cobalt ingots.

[0049] Step 2: Ruthenium ingots with a purity of 3N (99.9%) are vacuum distilled in a vacuum distillation furnace at a temperature of 2650℃ and a vacuum degree of 1×10⁻⁶. -3 Pa; then the distilled ruthenium ingot was vacuum arc-melted in an electric arc furnace at a vacuum degree of 1×10⁻⁶. -3 Pa yielded high-purity 4N (99.99%) ruthenium ingots.

[0050] Step 3: Take cobalt ingots and ruthenium ingots, both with a purity of 4N, mix them, and then vacuum melt them. Control the atomic ratio of cobalt to ruthenium to be 50%:50%, the vacuum melting temperature to be 2000℃, the melting time to be 3 hours, and the vacuum degree to be 1×10⁻⁶. -3 Pa, to obtain a cobalt-ruthenium alloy liquid, inject the cobalt-ruthenium alloy liquid into a disc-shaped graphite mold, and obtain a high-purity cobalt-ruthenium alloy ingot.

[0051] Step 4: The cobalt-ruthenium alloy round ingot obtained in Step 1 is subjected to multiple rotary hot rolling. After each rolling pass, the rolling direction is rotated by 120° for the next rolling pass. Each rolling pass consists of three passes, and the rolling process is repeated for three cycles. The hot rolling temperature is 950℃, and the hot rolling time is 10 minutes to obtain a cobalt-ruthenium alloy slab. After hot rolling, the total deformation of the cobalt-ruthenium alloy slab is 67.2%, the grain size is 120±20μm, and the proportion of grains with the (0001) orientation is 46.0%.

[0052] Step 5: Anneal the cobalt-ruthenium alloy slab at a temperature of 1000℃ for 3 hours to obtain a cobalt-ruthenium target.

[0053] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for preparing a cobalt-ruthenium target, characterized in that, The method includes the following steps: Step 1: The cobalt ingot with a purity of 2N8 (99.8%) is vacuum distilled once in a vacuum distillation furnace, then the cobalt ingot after the first distillation is vacuum distilled a second time, and finally the cobalt ingot is vacuum arc melted in an electric arc melting furnace to obtain high-purity 4N (99.99%) cobalt ingot. Step 2: Vacuum distillation of ruthenium ingot with a purity of 3N (99.9%) is carried out in a vacuum distillation furnace, and then the distilled ruthenium ingot is vacuum arc melted in an electric arc melting furnace to obtain high-purity 4N (99.99%) ruthenium ingot. Step 3: Take cobalt ingots and ruthenium ingots with a purity of 4N respectively, mix them and then perform vacuum melting to obtain cobalt-ruthenium alloy liquid. Pour the cobalt-ruthenium alloy liquid into a disc-shaped graphite mold to obtain high-purity cobalt-ruthenium alloy round ingots. Step 4: The cobalt-ruthenium alloy round ingot obtained in Step 3 is subjected to multiple rotary hot rolling at a rotation angle of 120° for 2 to 3 cycles to obtain a cobalt-ruthenium alloy slab. Step 5: Anneal the cobalt-ruthenium alloy slab to obtain a cobalt-ruthenium target; In step 4, after each rolling pass, the rolling direction is rotated 120° for the next rolling pass. Each three rolling passes constitute one cycle, and the rolling cycle is 2 to 3 cycles. In step 4, the total deformation of the hot-rolled cobalt-ruthenium alloy slab is 60%–80%, the grain size is 120±20μm, and the proportion of grains with (0001) orientation is 40%–60%. In step 4, the hot rolling temperature is 950–1350℃ and the hot rolling time is 8–20 min.

2. The method for preparing a cobalt-ruthenium target according to claim 1, characterized in that, In step 1, the temperature of the first distillation is 1500–1550℃, and the vacuum degree is 1×10⁻⁶. -2 Pa; the secondary distillation temperature is 1550–1600℃, and the vacuum is 1×10⁻⁶. -2 Pa; the vacuum degree of electric arc melting is 1×10 -3 Pa.

3. The method for preparing a cobalt-ruthenium target according to claim 1, characterized in that, In step 2, the distillation temperature is 2600–2700℃, and the vacuum degree is 1×10⁻⁶. -3 Pa; the vacuum degree of electric arc melting is 1×10 -3 Pa.

4. The method for preparing a cobalt-ruthenium target according to claim 1, characterized in that, In step 3, the atomic ratio of cobalt to ruthenium is (50%–80%):(20%–50%).

5. The method for preparing a cobalt-ruthenium target according to claim 1, characterized in that, In step 3, the vacuum melting temperature is 1600–2000℃, the melting time is 2–4 hours, and the vacuum degree is 1×10⁻⁶. -3 Pa.

6. The method for preparing a cobalt-ruthenium target according to claim 1, characterized in that, In step 5, the annealing temperature is 800–1000℃ and the annealing time is 2–4 hours.