Preparation method of ultrahigh-purity copper-aluminum alloy for integrated circuit

Abstract

The invention provides a preparation method of an ultrahigh-purity copper-aluminum alloy for an integrated circuit, and the preparation method comprises the following steps: (1) independently placing an ultrahigh-purity copper raw material and high-purity aluminum in a crucible and a feeding bin of a vacuum induction melting furnace, and carrying out vacuum induction melting to obtain an ultrahigh-purity copper-aluminum alloy intermediate; and (2) carrying out electron beam melting on the ultrahigh-purity copper-aluminum alloy intermediate obtained in the step (1) to obtain the ultrahigh-purity copper-aluminum alloy. By adopting the technology of coupling vacuum induction melting with electron beam melting, the preparation of the ultrahigh-purity copper-aluminum alloy is realized, the prepared alloy cast ingot is low in element loss and more uniform in distribution, the generation of particles is reduced, and the performance of the ultrahigh-purity copper-aluminum target prepared from the cast ingot can be kept stable in the sputtering process.

Description

Technical Field

[0001] The present invention belongs to the technical field of alloy target manufacturing, and relates to a preparation method of ultra-high purity copper-aluminum alloy for integrated circuits. Background Art

[0002] With the continuous development of chip manufacturing processes, due to the better electromigration resistance, electrical conductivity, and thermal conductivity of high-purity copper and copper alloys, traditional aluminum and aluminum alloy interconnects have been gradually replaced by copper and copper alloys. High-purity copper alloys are mainly applied in the 14-45 nm technology nodes. These alloys help prevent the diffusion of vacancies and Cu atoms in Cu interconnects in high-purity copper, and can greatly improve the electromigration resistance of interconnects.

[0003] Currently, high-purity copper-aluminum targets for integrated circuits are usually prepared by the melting and casting method. For example, copper is melted in a vacuum induction furnace and alloyed with aluminum, and then ingots are cast by gravity casting; or copper can be melted and alloyed with aluminum in a vacuum induction furnace and then directly cast into a mold.

[0004] CN115466862B discloses a melting process of ultra-high purity copper-aluminum alloy. The melting process includes: melting copper materials under vacuum, and then sequentially performing the first gas filling and adding the first aluminum material, the second gas filling and adding the second aluminum material, and the third gas filling and adding the third aluminum material, and then performing static refining. After the static refining is completed, casting is carried out. During the casting process, the mold vibrates, and then the ultra-high purity copper-aluminum alloy is obtained after cooling and demolding. However, this process has a cumbersome melting step, which is not conducive to improving production efficiency. In addition, shrinkage cavities are likely to occur inside the ingot during direct melting casting or pouring, which affects the final target processing. In addition, in order to have good casting fluidity, usually a very high casting temperature is required. A very high casting temperature will have a relatively large impact on the crucible of the vacuum induction equipment. There is a risk that the components of the crucible (usually a graphite crucible) at high temperatures will be introduced into the copper alloy ingot, and particles will be generated during the use of the target, resulting in a low yield of the wafer.

[0005] Aiming at the problems of poor uniformity of aluminum mass content and more particles in the ultra-high purity copper-aluminum alloy obtained by the prior art, which affect the performance of subsequent products. Therefore, there is an urgent need to develop a preparation method of ultra-high purity copper-aluminum alloy with uniform distribution of alloy elements and few particles. Summary of the Invention

[0006] Aiming at the deficiencies of the prior art, the purpose of the present invention is to provide a preparation method of ultra-high purity copper-aluminum alloy for integrated circuits. By adopting the technology of vacuum induction melting coupled with electron beam melting, the preparation of ultra-high purity copper-aluminum alloy is realized. The obtained alloy ingot has less element loss and more uniform distribution, and reduces the generation of particles, which can ensure the stability of the performance during the sputtering process of the ultra-high purity copper-aluminum target prepared from the ingot.

[0007] To achieve the object of the present invention, the following technical solutions are adopted in the present invention:

[0008] The present invention provides a preparation method of ultra-high purity copper-aluminum alloy for integrated circuits, and the preparation method includes the following steps:

[0009] (1) Independently place the ultra-high purity copper raw material and high-purity aluminum in the crucible and the feeding bin of a vacuum induction melting furnace, and perform vacuum induction melting to obtain an ultra-high purity copper-aluminum alloy intermediate;

[0010] (2) Perform electron beam melting on the ultra-high purity copper-aluminum alloy intermediate obtained in step (1) to obtain an ultra-high purity copper-aluminum alloy.

[0011] In the preparation method provided by the present invention, pre-alloying is first carried out by vacuum induction melting, and then secondary melting is carried out by electron beam melting. Because the specific melting temperature of vacuum induction melting and the high-vacuum environment during the electron beam secondary melting process are beneficial to reducing the solubility of gas impurity elements in the melt, thereby promoting the removal of impurities. At the same time, vacuum induction melting can pre-uniformly distribute alloy elements, avoiding the problem that it is not easy to achieve alloy homogenization when using electron beam melting alone. In addition, the electron beam has concentrated energy and good controllability, and can achieve precise positioning of the melting position. Since the crucible containers used in electron beam melting are all oxygen-free copper, it is not easy to introduce particulate matter, and it is beneficial to reduce the particulate matter introduced during the raw material and pre-alloying process during the electron beam melting process. Therefore, by using vacuum induction melting and electron beam melting in combination, the problems of uneven distribution of alloy elements and increased particulate matter in high-purity copper-aluminum alloy in the prior art are solved, ensuring that the performance remains stable during the sputtering process of the ultra-high purity copper-aluminum target prepared from the ingot.

[0012] As a preferred technical solution of the present invention, the ultra-high purity copper raw material described in step (1) includes ultra-high purity copper electrolytic sheets.

[0013] Preferably, the purity of the ultra-high purity copper electrolytic sheet is ≥6N.

[0014] Preferably, the purity of the high-purity aluminum described in step (1) is ≥5N5.

[0015] Preferably, the aluminum content in the ultra-high purity copper-aluminum alloy intermediate described in step (1) is 0.05 wt% - 1.00 wt%.

[0016] As a preferred technical solution of the present invention, before the vacuum induction melting described in step (1), it also includes evacuating the vacuum induction melting furnace to a vacuum degree ≤10 -3 Pa.

[0017] Preferably, the operation of the vacuum induction melting described in step (1) includes:

[0018] The ultra-high purity copper raw material is subjected to first melting to obtain a copper solution. Subsequently, a protective gas is introduced and high-purity aluminum is added to the copper solution, and then second melting and cooling are carried out in sequence.

[0019] As a preferred technical solution of the present invention, the temperature of the first melting is 1160 - 1260 °C.

[0020] Preferably, the heat preservation time of the first melting is 40 - 90 min.

[0021] Preferably, the temperature of the second melting is the same as that of the first melting.

[0022] Preferably, the heat preservation time of the second melting is 40 - 90 min.

[0023] As a preferred technical solution of the present invention, after the vacuum induction melting in step (1), machining, pickling, water washing and drying are also carried out in sequence.

[0024] As a preferred technical solution of the present invention, the electron beam melting in step (2) is carried out in an electron beam melting furnace.

[0025] Preferably, before the electron beam melting in step (2), the ultra-high purity copper-aluminum alloy intermediate in step (1) is fixed in the loading bin of the electron beam melting furnace.

[0026] Preferably, after the fixation of the ultra-high purity copper-aluminum alloy intermediate and before the electron beam melting in step (2), it also includes evacuating the electron beam melting furnace to a vacuum degree ≤ 10 -3 Pa.

[0027] As a preferred technical solution of the present invention, the electron beam melting in step (2) is carried out using a double electron gun.

[0028] Preferably, the operation of the electron beam melting in step (2) includes:

[0029] After preheating the double electron gun, turn on the first electron gun for a first bombardment. When the ultra-high purity copper-aluminum alloy intermediate starts to melt and drips into the cold hearth and stands still, turn on the second electron gun for a second bombardment, and then draw out the ultra-high purity copper-aluminum alloy solution.

[0030] As a preferred technical solution of the present invention, the power of the first electron gun is 200 - 350 kW.

[0031] Preferably, the power of the second electron gun is 200 - 350 kW.

[0032] Preferably, the standing time is 2 - 5 min.

[0033] Preferably, the voltage of the electron beam melting in step (2) is 25 - 40 kV.

[0034] Preferably, the current of the electron beam melting in step (2) is 6 - 12 A.

[0035] Preferably, the rate of the dummy bar is 15 - 25 mm / min.

[0036] As a preferred technical solution of the present invention, the aluminum content in the ultra-high purity copper-aluminum alloy in step (2) is 0.05 wt% - 1.00 wt%.

[0037] Preferably, the number of particles with a particle size > 0.5 μm in the ultra-high purity copper-aluminum alloy in step (2) is < 2000 pieces / g.

[0038] As a preferred technical solution of the present invention, the preparation method includes the following steps:

[0039] (1) Independently place the ultra-high purity copper raw material with a purity ≥ 6N and the high-purity aluminum with a purity ≥ 5N5 in the crucible and the feeding bin of the vacuum induction melting furnace respectively, and evacuate the vacuum induction melting furnace to a vacuum degree ≤ 10 -3 Pa, then carry out vacuum induction melting, and then successively carry out machining, pickling, water washing and drying to obtain an ultra-high purity copper-aluminum alloy intermediate with an aluminum content of 0.05 wt% - 1.00 wt%;

[0040] The operations of the vacuum induction melting include: first melting the ultra-high purity copper raw material at a temperature of 1160 - 1260 °C and holding for 40 - 90 min to obtain a copper solution, then filling with a protective gas and adding the high-purity aluminum into the copper solution, carrying out second melting and holding for 40 - 90 min, and then cooling; the temperature of the second melting is the same as that of the first melting;

[0041] (2) Fix the ultra-high purity copper-aluminum alloy intermediate obtained in step (1) in the loading bin of the electron beam melting furnace, and evacuate the electron beam melting furnace to a vacuum degree ≤ 10 -3 Pa, then carry out electron beam melting at a voltage of 25 - 40 kV and a current of 6 - 12 A to obtain an ultra-high purity copper-aluminum alloy with an aluminum content of 0.05 wt% - 1.00 wt% and the number of particles with a particle size > 0.5 μm < 2000 pieces / g;

[0042] The operations of the electron beam melting include: after preheating the double electron guns, turn on the first electron gun and gradually increase the power to 200 - 350 kW for the first bombardment. When the intermediate of the ultra-high purity copper-aluminum alloy starts to melt and drips into the cold hearth and stands still for 2 - 5 minutes, turn on the second electron gun and gradually increase the power to 200 - 350 kW for the second bombardment. Subsequently, draw the ingot of the ultra-high purity copper-aluminum alloy solution at a rate of 15 - 25 mm / min.

[0043] Compared with the prior art, the present invention has the following beneficial effects:

[0044] (1) The preparation method provided by the present invention realizes the preparation of the ultra-high purity copper-aluminum alloy by adopting the technology of vacuum induction melting coupled with electron beam melting and combining the control of the relevant parameters of the above process. The prepared alloy ingot has less element loss, more uniform distribution, and reduced generation of particulate matter, which can ensure the stable performance during the sputtering process of the ultra-high purity copper-aluminum target prepared from the ingot. Among them, the prepared ultra-high purity copper-aluminum alloy has less element loss, and the number of particulate matters with a particle size > 0.5 μm is < 2000 pieces / g;

[0045] (2) The preparation method provided by the present invention is simple in operation, does not require complex equipment, and is suitable for large-scale industrial applications. Specific Embodiments

[0046] The technical solution of the present invention will be further described below through specific embodiments. Those skilled in the art should understand that the embodiments are only for helping to understand the present invention and should not be regarded as specific limitations to the present invention.

[0047] The specific embodiments of the present invention provide a method for preparing an ultra-high purity copper-aluminum alloy for integrated circuits, and the preparation method includes the following steps:

[0048] (1) Independently place the ultra-high purity copper raw material and high-purity aluminum in the crucible and the feeding bin of the vacuum induction melting furnace respectively, and carry out vacuum induction melting to obtain an intermediate of the ultra-high purity copper-aluminum alloy;

[0049] (2) Carry out electron beam melting on the intermediate of the ultra-high purity copper-aluminum alloy obtained in step (1) to obtain the ultra-high purity copper-aluminum alloy.

[0050] In some embodiments of the present invention, the ultra-high purity copper raw material in step (1) includes ultra-high purity copper electrolytic sheets.

[0051] In some embodiments of the present invention, the purity of the ultra-high purity copper electrolytic sheet is ≥ 6N, for example, it can be 6N1, 6N2, 6N3, 6N4, 6N5, 6N6, 6N7, 6N8 or 6N9, etc., but not limited to the listed values, and other unlisted values within the numerical range are equally applicable.

[0052] In some embodiments of the present invention, the purity of the high-purity aluminum in step (1) is ≥5N5. For example, it can be 5N6, 5N7, 5N8, 5N9, 6N, 6N1, 6N2, 6N3 or 6N5, etc., but is not limited to the listed values. Other unlisted values within the numerical range are equally applicable.

[0053] In some embodiments of the present invention, the aluminum content in the ultra-high purity copper-aluminum alloy intermediate in step (1) is 0.05 wt% - 1.00 wt%. For example, it can be 0.06 wt%, 0.08 wt%, 0.10 wt%, 0.20 wt%, 0.30 wt%, 0.40 wt%, 0.50 wt%, 0.60 wt%, 0.70 wt%, 0.80 wt% or 0.90 wt%, etc., but is not limited to the listed values. Other unlisted values within the numerical range are equally applicable.

[0054] Since basically no aluminum loss occurs during the preparation process of the present invention, there is no need to additionally increase the proportion of aluminum. That is to say, the aluminum content in the ultra-high purity copper-aluminum alloy intermediate is the proportion of high-purity aluminum in the total raw material addition when the raw materials are added.

[0055] In some embodiments of the present invention, before the vacuum induction melting in step (1), it further includes evacuating the vacuum induction melting furnace to a vacuum degree ≤10 -3 Pa.

[0056] In some embodiments of the present invention, the operation of the vacuum induction melting in step (1) includes:

[0057] First melting the ultra-high purity copper raw material to obtain a copper solution, then filling with a protective gas and adding high-purity aluminum to the copper solution, and then performing second melting and cooling in sequence.

[0058] Exemplarily, the protective gas includes argon.

[0059] In some embodiments of the present invention, the temperature of the first melting is 1160 - 1260 °C. For example, it can be 1170 °C, 1180 °C, 1190 °C, 1200 °C, 1210 °C, 1220 °C, 1230 °C, 1240 °C or 1250 °C, etc., but is not limited to the listed values. Other unlisted values within the numerical range are equally applicable.

[0060] It is worth noting that by controlling the temperature range of the first melting, the gases in the copper solution are ensured to be removed and carbon particles are avoided from being introduced, thereby avoiding affecting the performance of the ultra-high purity copper-aluminum alloy.

[0061] In some embodiments of the present invention, the heat preservation time of the first melting is 40 - 90 min. For example, it can be 45 min, 50 min, 55 min, 60 min, 65 min, 70 min, 75 min, 80 min, or 85 min, etc., but is not limited to the listed values. Other unlisted values within the numerical range are equally applicable.

[0062] In some embodiments of the present invention, the temperature of the second melting is the same as that of the first melting.

[0063] In some embodiments of the present invention, the heat preservation time of the second melting is 40 - 90 min. For example, it can be 45 min, 50 min, 55 min, 60 min, 65 min, 70 min, 75 min, 80 min, or 85 min, etc., but is not limited to the listed values. Other unlisted values within the numerical range are equally applicable.

[0064] In some embodiments of the present invention, after the vacuum induction melting in step (1), machining, pickling, water washing, and drying are sequentially carried out.

[0065] Exemplarily, the machining includes turning the surface of the ultra-high purity copper-aluminum alloy intermediate and dividing it into small pieces.

[0066] It should be noted that no specific limitations are imposed on the pickling solution used for pickling and the related parameters for drying. Those skilled in the art can carry out according to the methods provided in the prior art or according to actual production experience.

[0067] In some embodiments of the present invention, the electron beam melting in step (2) is carried out in an electron beam melting furnace.

[0068] In some embodiments of the present invention, before the electron beam melting in step (2), the ultra-high purity copper-aluminum alloy intermediate in step (1) is fixed in the loading bin of the electron beam melting furnace.

[0069] In some embodiments of the present invention, after the fixation of the ultra-high purity copper-aluminum alloy intermediate and before the electron beam melting in step (2), it further includes evacuating the electron beam melting furnace to a vacuum degree ≤ 10 -3 Pa.

[0070] In some embodiments of the present invention, the electron beam melting in step (2) is carried out using a double electron gun.

[0071] In some embodiments of the present invention, the operations of the electron beam melting in step (2) include:

[0072] After preheating the dual electron guns, turn on the first electron gun for a bombardment. When the ultra-high purity copper-aluminum alloy intermediate begins to melt and drips into the cooling bed for standing, turn on the second electron gun for a second bombardment, and then the ultra-high purity copper-aluminum alloy solution is guided into ingots.

[0073] It is worth noting that the electron beam melting of the present invention further purifies the inclusions and gases in the raw materials, and simultaneously utilizes dual electron guns to complete the two processes of melting and refining in the same equipment, which not only improves the melting efficiency but also reduces the mixing of impurities.

[0074] In some embodiments of the present invention, the power of the first electron gun is 200-350 kW, for example, 220 kW, 240 kW, 250 kW, 260 kW, 280 kW, 300 kW, 320 kW or 340 kW, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0075] In some embodiments of the present invention, the power of the second electron gun is 200-350 kW, for example, 220 kW, 240 kW, 250 kW, 260 kW, 280 kW, 300 kW, 320 kW or 340 kW, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0076] It is worth noting that by adjusting the power of the first electron gun and the second electron gun to adjust the energy of the electron beam spot emitted, the heating temperature of the ultra-high purity copper-aluminum alloy intermediate and solution can be adjusted. If the power of the first electron gun is too low, the intermediate cannot be fully melted; if the power of the first electron gun is too high, it is easy to cause the alloy material to volatilize or the composition to be uneven. If the power of the second electron gun is too low, premature cooling is likely to occur during the subsequent ingot introduction process; if the power of the second electron gun is too high, the metal material in the copper-aluminum alloy liquid will volatilize and burn severely, which will increase the metal loss in the ultra-high purity copper-aluminum alloy and reduce the yield rate.

[0077] In some embodiments of the present invention, the standing time is 2-5 minutes, for example, it can be 2.5 minutes, 3 minutes, 3.5 minutes, 4 minutes, 4.5 minutes or 5 minutes, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0078] It is worth noting that by allowing the alloy liquid to stay in the cooling bed for a certain period of time, the gas in the alloy liquid can be fully released.

[0079] In some embodiments of the present invention, the voltage of the electron beam melting in step (2) is 25 - 40 kV. For example, it can be 26 kV, 28 kV, 30 kV, 32 kV, 35 kV, 36 kV, 38 kV, etc., but is not limited to the listed values. Other unlisted values within the numerical range are equally applicable.

[0080] In some embodiments of the present invention, the current of the electron beam melting in step (2) is 6 - 12 A. For example, it can be 6.5 A, 7 A, 7.5 A, 8 A, 8.5 A, 9 A, 9.5 A, 10 A, 10.5 A, 11 A, 11.5 A, etc., but is not limited to the listed values. Other unlisted values within the numerical range are equally applicable.

[0081] In some embodiments of the present invention, the rate of the dummy bar is 15 - 25 mm / min. For example, it can be 16 mm / min, 17 mm / min, 18 mm / min, 19 mm / min, 20 mm / min, 21 mm / min, 22 mm / min, 23 mm / min, 24 mm / min, etc., but is not limited to the listed values. Other unlisted values within the numerical range are equally applicable.

[0082] In some embodiments of the present invention, the aluminum content in the ultra-high purity copper-aluminum alloy in step (2) is 0.05 wt% - 1.00 wt%. For example, it can be 0.06 wt%, 0.08 wt%, 0.10 wt%, 0.20 wt%, 0.30 wt%, 0.40 wt%, 0.50 wt%, 0.60 wt%, 0.70 wt%, 0.80 wt%, 0.90 wt%, etc., but is not limited to the listed values. Other unlisted values within the numerical range are equally applicable.

[0083] In some embodiments of the present invention, the number of particles with a particle size > 0.5 μm in the ultra-high purity copper-aluminum alloy in step (2) is < 2000 particles / g.

[0084] Unless otherwise defined, the technical terms used in the following examples and comparative examples have the same meanings as commonly understood by those skilled in the art to which the present invention pertains. The raw materials, instruments, equipment, etc. used in the following examples and comparative examples can all be obtained through market purchase or by existing methods; the experimental methods, unless otherwise specified, are all conventional methods. In the following examples and comparative examples, the pickling process uses nitric acid with a concentration of 30 wt% as the pickling solution.

[0085] Example 1

[0086] This example provides a method for preparing an ultra-high purity copper-aluminum alloy for integrated circuits, and the preparation method includes the following steps:

[0087] (1) Independently place an ultra-high purity copper electrolytic sheet with a purity of 6N2 and high-purity aluminum with a purity of 5N7 in the crucible and the feeding bin of the melting furnace respectively, and evacuate the vacuum induction melting furnace to a vacuum degree of 4×10 -4 Pa, then carry out vacuum induction melting, and then turn the surface of the ingot obtained by turning and cut it into small pieces. Finally, carry out pickling, water washing and drying in sequence to obtain an ultra-high purity copper-aluminum alloy intermediate with an aluminum content of 0.10 wt%;

[0088] Among them, the operation of the vacuum induction melting includes: first melting the ultra-high purity copper electrolytic sheet at a temperature of 1200°C and holding for 60 minutes to obtain a copper solution, then filling argon and adding high-purity aluminum into the copper solution, carrying out second melting and holding for 60 minutes, and then cooling; the temperature of the second melting is the same as that of the first melting;

[0089] (2) Fix the ultra-high purity copper-aluminum alloy intermediate described in step (1) in the loading bin of the electron beam melting furnace, and evacuate the electron beam melting furnace to a vacuum degree of 4×10 -4 Pa, and then carry out electron beam melting at a voltage of 35 kV and a current of 9 A to obtain an ultra-high purity copper-aluminum alloy;

[0090] Among them, the operation of the electron beam melting includes: after preheating the double electron guns, turn on the first electron gun and gradually increase the power to 280 kW for the first bombardment. When the ultra-high purity copper-aluminum alloy intermediate begins to melt and drops into the cold bed and stands for 3 minutes, turn on the second electron gun and gradually increase the power to 280 kW for the second bombardment. Then draw the ultra-high purity copper-aluminum alloy solution at a rate of 20 mm / min, and finally turn off the double electron guns and the vacuum device in sequence.

[0091] Example 2

[0092] This example provides a preparation method of an ultra-high purity copper-aluminum alloy for integrated circuits. The preparation method includes the following steps:

[0093] (1) Independently place an ultra-high purity copper electrolytic sheet with a purity of 6N5 and high-purity aluminum with a purity of 5N5 in the crucible and the feeding bin of the melting furnace respectively, and evacuate the vacuum induction melting furnace to a vacuum degree of 1×10 -3 Pa, then carry out vacuum induction melting, and then turn the surface of the ingot obtained by turning and cut it into small pieces. Finally, carry out pickling, water washing and drying in sequence to obtain an ultra-high purity copper-aluminum alloy intermediate with an aluminum content of 0.50 wt%;

[0094] Among them, the operations of the vacuum induction melting include: first melting the ultra-high purity copper electrolytic sheet at a temperature of 1160 °C and holding for 90 min to obtain a copper solution, then filling with argon and adding high-purity aluminum into the copper solution, performing second melting and holding for 80 min, and then cooling; the temperature of the second melting is the same as that of the first melting;

[0095] (2) Fix the ultra-high purity copper-aluminum alloy intermediate described in step (1) in the charging bin of the electron beam melting furnace, and evacuate the electron beam melting furnace to a vacuum degree of 1×10 -3 Pa, and then perform electron beam melting at a voltage of 25 kV and a current of 8 A to obtain an ultra-high purity copper-aluminum alloy;

[0096] Among them, the operations of the electron beam melting include: after preheating the double electron guns, turn on the first electron gun and gradually increase the power to 350 kW for the first bombardment. When the ultra-high purity copper-aluminum alloy intermediate starts to melt and drops into the cold hearth and stands for 5 min, turn on the second electron gun and gradually increase the power to 350 kW for the second bombardment. Then, draw the ingot of the ultra-high purity copper-aluminum alloy solution at a rate of 25 mm / min, and finally turn off the double electron guns and the vacuum device in sequence.

[0097] Example 3

[0098] This example provides a preparation method of an ultra-high purity copper-aluminum alloy for integrated circuits. The preparation method includes the following steps:

[0099] (1) Independently place the ultra-high purity copper electrolytic sheet with a purity of 6N2 and the high-purity aluminum with a purity of 5N9 in the crucible and the feeding bin of the melting furnace, and evacuate the vacuum induction melting furnace to a vacuum degree of 1×10 -3 Pa, then perform vacuum induction melting, and then turn the surface of the cast ingot obtained by turning and cut it into small pieces. Finally, perform pickling, water washing and drying in sequence to obtain an ultra-high purity copper-aluminum alloy intermediate with an aluminum content of 0.05 wt%;

[0100] Among them, the operations of the vacuum induction melting include: first melting the ultra-high purity copper electrolytic sheet at a temperature of 1260 °C and holding for 40 min to obtain a copper solution, then filling with argon and adding high-purity aluminum into the copper solution, performing second melting and holding for 50 min, and then cooling; the temperature of the second melting is the same as that of the first melting;

[0101] (2) Fix the ultra-high purity copper-aluminum alloy intermediate described in step (1) in the charging bin of the electron beam melting furnace, and evacuate the electron beam melting furnace to a vacuum degree of 1×10 -3 Pa, and then perform electron beam melting at a voltage of 40 kV and a current of 10 A to obtain an ultra-high purity copper-aluminum alloy;

[0102] Among them, the operations of the electron beam melting include: after preheating the double electron guns, turn on the first electron gun and gradually increase the power to 200 kW for a first bombardment. When the intermediate of the ultra-high purity copper-aluminum alloy starts to melt and drops into the cold hearth and stands still for 2 min, turn on the second electron gun and gradually increase the power to 200 kW for a second bombardment. Subsequently, draw the ultra-high purity copper-aluminum alloy solution at a rate of 15 mm / min, and finally turn off the double electron guns and the vacuum device in sequence.

[0103] Example 4

[0104] This example provides a method for preparing an ultra-high purity copper-aluminum alloy for integrated circuits. Except that the temperature of the first melting in step (1) is 1100 °C, other conditions are the same as those in Example 1.

[0105] Example 5

[0106] This example provides a method for preparing an ultra-high purity copper-aluminum alloy for integrated circuits. Except that the temperature of the first melting in step (1) is 1300 °C, other conditions are the same as those in Example 1.

[0107] Example 6

[0108] This example provides a method for preparing an ultra-high purity copper-aluminum alloy for integrated circuits. Except that the heat preservation time of the second melting in step (1) is 20 min, other conditions are the same as those in Example 1.

[0109] Example 7

[0110] This example provides a method for preparing an ultra-high purity copper-aluminum alloy for integrated circuits. Except that the heat preservation time of the second melting in step (1) is 120 min, other conditions are the same as those in Example 1.

[0111] Example 8

[0112] This example provides a method for preparing an ultra-high purity copper-aluminum alloy for integrated circuits. Except that the power of the first electron gun in step (2) is 150 kW, other conditions are the same as those in Example 1.

[0113] Example 9

[0114] This example provides a method for preparing an ultra-high purity copper-aluminum alloy for integrated circuits. Except that the power of the first electron gun in step (2) is 400 kW, other conditions are the same as those in Example 1.

[0115] Example 10

[0116] This embodiment provides a method for preparing ultra-high purity copper-aluminum alloy for integrated circuits. Except that the power of the second electron gun described in step (2) is 150 kW, other conditions are the same as those in Embodiment 1.

[0117] Embodiment 11

[0118] This embodiment provides a method for preparing ultra-high purity copper-aluminum alloy for integrated circuits. Except that the power of the second electron gun described in step (2) is 400 kW, other conditions are the same as those in Embodiment 1.

[0119] Embodiment 12

[0120] This embodiment provides a method for preparing ultra-high purity copper-aluminum alloy for integrated circuits. Except that it is left to stand in the cold hearth for 1 min in step (2), other conditions are the same as those in Embodiment 1.

[0121] Comparative Example 1

[0122] This comparative example provides a method for preparing ultra-high purity copper-aluminum alloy for integrated circuits. Except that vacuum induction melting is replaced by hot isostatic pressing after crushing the raw materials, other conditions are the same as those in Embodiment 1.

[0123] Comparative Example 2

[0124] This comparative example provides a method for preparing ultra-high purity copper-aluminum alloy for integrated circuits. Except that electron beam melting is replaced by conventional casting, other conditions are the same as those in Embodiment 1.

[0125] The aluminum content, aluminum element distribution, number of particles with particle size > 0.5 μm, and contents of impurity oxygen element and chlorine element in the ultra-high purity copper-aluminum alloy prepared in the above embodiments and comparative examples are tested. The test methods are as follows: The aluminum content and aluminum element distribution are tested by inductively coupled plasma optical emission spectrometer (ICP-OES). Sampling is carried out from different positions of the ultra-high purity copper-aluminum alloy to test its aluminum content. If the aluminum contents at each position are consistent, it is considered that the aluminum element distribution in the ultra-high purity copper-aluminum alloy is uniform; if the aluminum contents at each position are inconsistent, it is considered that the aluminum element distribution in the ultra-high purity copper-aluminum alloy is non-uniform. The number of particles with particle size > 0.5 μm is tested by an insoluble particle detector (LPC); the contents of impurity oxygen element and chlorine element are tested by glow discharge mass spectrometry (GDMS). The above test results are shown in Table 1.

[0126] Table 1

[0127]

[0128]

[0129] As can be seen from Table 1:

[0130] (1) The preparation method provided in Examples 1-3 of the present invention adopts the technology of vacuum induction melting coupled with electron beam melting, and the loss of aluminum in the obtained ultra-high purity copper-aluminum alloy is very small, and the aluminum element is evenly distributed, and the content of particle inclusions and impurities is also greatly reduced, wherein the number of particles with a particle size greater than 0.5 μm is less than 1500 pieces / g, the Cl element content is less than 0.01 ppm, and the O element content is less than 1 ppm;

[0131] (2) It can be seen from the comparison between Example 1 and Examples 4-5 that when the temperature of the first melting is low, it is not conducive to removing gas impurities, resulting in a high content of Cl; when the temperature of the first melting is high, carbon particles are easily introduced, resulting in an increase in the number of carbon particles in the alloy;

[0132] (3) It can be seen from the comparison between Example 1 and Examples 6-7 that when the holding time of the second melting is short, not only does the problem of uneven mixing of aluminum and copper exist, resulting in uneven distribution of alloy components, but also inclusions remain, which in turn affects subsequent target material processing; when the holding time of the second melting is long, not only does the risk of introducing particles increase, but it is also not conducive to extending the service life of the equipment;

[0133] (4) By comparing Example 1 with Examples 8-9, it can be seen that when the power of the first electron gun in electron beam melting is low, the intermediate cannot be fully melted, which not only makes it difficult to remove the Cl element, but also introduces more particulate matter; when the power of the first electron gun in electron beam melting is high, it is easy to cause the alloy material to volatilize or the composition to be uneven; by comparing Example 1 with Examples 10-11, it can be seen that when the power of the second electron gun in electron beam melting is low, premature cooling is likely to occur during the subsequent ingot introduction process, resulting in defects such as holes in the ingot, while increasing the introduction of particulate matter and poor uniformity of the aluminum element; when the power of the second electron gun in electron beam melting is high, the metal material in the copper-aluminum alloy liquid volatilizes and burns severely, thereby increasing the metal loss in the ultra-high purity copper-aluminum alloy and reducing the yield rate;

[0134] (5) It can be seen from the comparison between Example 1 and Example 12 that when the alloy liquid stays in the cooling bed for too short a time, it is not conducive to the escape of gas impurities, resulting in an increase in the Cl content in the ultra-high purity copper-aluminum alloy;

[0135] (6) From the comparison between Example 1 and Comparative Example 1, it can be seen that if the powderization hot isostatic pressing pre-alloying process is performed first, oxidation is easy to cause excessive gas elements, and there is also uneven mixing. When electron beam melting is performed, alloy element segregation is easy to occur. In addition, its production process is more complicated than vacuum induction melting, which is not conducive to production.

[0136] (6) By comparing Example 1 and Comparative Example 2 comprehensively, it can be seen that when conventional casting is used to replace electron beam melting, shrinkage cavities are likely to occur inside the ingot, which will in turn affect the subsequent processing and quality of the target material.

[0137] The applicant declares that the above description is only a specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Those skilled in the art should understand that any changes or substitutions that can be easily conceived by any person skilled in the art within the technical scope disclosed by the present invention fall within the protection scope and the disclosure scope of the present invention.

Claims

1. A method for preparing an ultra-high purity copper-aluminum alloy for integrated circuits, characterized in that: The preparation method comprises the following steps: (1) placing an ultra-high purity copper raw material and high purity aluminum in a crucible and a charging bin of a vacuum induction melting furnace, respectively, and performing vacuum induction melting to obtain an ultra-high purity copper-aluminum alloy intermediate; (2) Electron beam melting the ultra-high purity copper-aluminum alloy intermediate described in step (1) to obtain an ultra-high purity copper-aluminum alloy.

2. The preparation method according to claim 1, characterized in that: The ultra-high purity copper raw material in step (1) comprises an ultra-high purity copper electrolytic sheet; Preferably, the purity of the ultra-high purity copper electrolytic sheet is ≥6N; Preferably, the purity of the high-purity aluminum in step (1) is ≥5N5; Preferably, the aluminum content in the ultra-high purity copper-aluminum alloy intermediate in step (1) is 0.05wt%-1.00wt%.

3. The preparation method according to claim 1 or 2, characterized in that: Before the vacuum induction melting in step (1), the vacuum induction melting furnace is evacuated to a vacuum degree of ≤10 -3 Pa; Preferably, the vacuum induction melting operation in step (1) includes: The ultra-high purity copper raw material is first melted to obtain a copper solution, and then a protective gas is filled and high purity aluminum is added to the copper solution, and then a second melting and cooling are performed in sequence.

4. The preparation method according to claim 3, characterized in that: The first melting temperature is 1160-1260°C; Preferably, the first melting holding time is 40-90 min; Preferably, the temperature of the second melting is the same as the temperature of the first melting; Preferably, the second melting holding time is 40-90 min.

5. The preparation method according to any one of claims 1 to 4, characterized in that: After the vacuum induction melting in step (1), machining, pickling, water washing and drying are carried out in sequence.

6. The preparation method according to any one of claims 1 to 5, characterized in that: The electron beam melting in step (2) is carried out in an electron beam melting furnace; Preferably, before the electron beam melting in step (2), the ultra-high purity copper-aluminum alloy intermediate in step (1) is fixed in a charging bin of an electron beam melting furnace; Preferably, after the ultra-high purity copper-aluminum alloy intermediate is fixed and before the electron beam melting in step (2), the electron beam melting furnace is evacuated to a vacuum degree of ≤10 -3 Pa.

7. The preparation method according to any one of claims 1 to 6, characterized in that: The electron beam melting in step (2) is performed using a dual electron gun; Preferably, the electron beam melting operation in step (2) includes: After preheating the dual electron guns, turn on the first electron gun for a bombardment. When the ultra-high purity copper-aluminum alloy intermediate begins to melt and drips into the cooling bed for standing, turn on the second electron gun for a second bombardment, and then the ultra-high purity copper-aluminum alloy solution is guided into ingots.

8. The preparation method according to claim 7, characterized in that: The power of the first electron gun is 200-350kW; Preferably, the power of the second electron gun is 200-350 kW; Preferably, the standing time is 2-5 min; Preferably, the voltage of the electron beam melting in step (2) is 25-40 kV; Preferably, the current of the electron beam melting in step (2) is 6-12A; Preferably, the speed of the ingot drawing is 15-25 mm / min.

9. The preparation method according to any one of claims 1 to 8, characterized in that: The aluminum content in the ultra-high purity copper-aluminum alloy in step (2) is 0.05wt%-1.00wt%; Preferably, the number of particles with a particle size greater than 0.5 μm in the ultra-high purity copper-aluminum alloy in step (2) is less than 2000 particles / g.

10. The preparation method according to any one of claims 1 to 9, characterized in that: The preparation method comprises the following steps: (1) Ultra-high purity copper raw materials with a purity of ≥6N and high purity aluminum with a purity of ≥5N5 are placed in the crucible and charging bin of a vacuum induction melting furnace respectively, and the vacuum induction melting furnace is evacuated to a vacuum degree of ≤10 -3 Pa, followed by vacuum induction melting, and then machining, pickling, water washing and drying in sequence to obtain an ultra-high purity copper-aluminum alloy intermediate with an aluminum content of 0.05wt%-1.00wt%; The vacuum induction melting operation includes: first melting the ultra-high purity copper raw material at a temperature of 1160-1260° C. and keeping the temperature for 40-90 minutes to obtain a copper solution, then filling the copper solution with a protective gas and adding high purity aluminum to the copper solution, second melting and keeping the temperature for 40-90 minutes, and then cooling; the temperature of the second melting is the same as the temperature of the first melting; (2) The ultra-high purity copper-aluminum alloy intermediate of step (1) is fixed in the charging bin of the electron beam melting furnace, and the electron beam melting furnace is evacuated to a vacuum degree of ≤10 -3 Pa, and then electron beam melting is performed at a voltage of 25-40 kV and a current of 6-12 A to obtain an ultra-high purity copper-aluminum alloy having an aluminum content of 0.05 wt%-1.00 wt% and a particle size of >0.5 μm and a number of particles <2000 / g; The electron beam melting operation includes: after preheating the dual electron guns, starting the first electron gun and gradually increasing the power to 200-350 kW for a bombardment, when the ultra-high purity copper-aluminum alloy intermediate begins to melt and drips into the cooling bed and stands for 2-5 minutes, starting the second electron gun and gradually increasing the power to 200-350 kW for a second bombardment, and then guiding the ultra-high purity copper-aluminum alloy solution at a rate of 15-25 mm / min.

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