Preparation method of high homogeneity and high stability copper target material

Abstract

The application discloses a preparation method of high-homogeneity and high-stability copper target material, and the method comprises the following steps: firstly, cutting off the riser of high-purity copper ingot and turning to obtain pretreated high-purity copper ingot; secondly, putting the pretreated high-purity copper ingot into a furnace to heat and keep warm, and then forging to obtain forged copper blank; thirdly, carrying out room temperature circumferential rolling treatment on the forged copper blank to obtain rolled copper blank; fourthly, carrying out double-stage annealing heat treatment on the rolled copper blank to obtain copper target blank; and finally, machining, cleaning and packaging to obtain high-homogeneity and high-stability copper target material. The high-purity copper ingot is sequentially subjected to pretreatment, forging, room temperature circumferential rolling, double-stage annealing, machining and cleaning and packaging, so that high-quality copper target material with uniform structure, controllable crystal orientation and excellent thermal stability is prepared, the quality of sputtering film is improved, the method is simple in operation, high in controllability and high in production efficiency, raw materials and production cost are saved, and the method is suitable for wide range of popularization and application.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of sputtering target material preparation, and particularly relates to a preparation method of high-homogeneity high-stability copper target material. BACKGROUND

[0002] Sputtering film coating technology is a technology that uses high-speed particles to bombard the surface of a target material under vacuum conditions, and finally the bombarded particles are deposited on a substrate. In other words, sputtering film coating technology is used to realize the preparation of various thin films by using the sputtering phenomenon. Compared with traditional vacuum evaporation, sputtering film coating has many advantages, such as strong adhesion between the film layer and the substrate, high uniformity of the film layer, high controllability of the composition of the film layer, and easy industrial production. Therefore, sputtering film coating technology plays an important role in the discovery of new materials, the development of new functions, and the application of new devices. Among them, the magnetron sputtering film coating technology can achieve high-speed deposition under low-temperature and low-loss conditions, and is widely used in high-tech industries such as semiconductors, photovoltaics, flat panel displays, and information storage.

[0003] Compared with aluminum, copper target material has lower resistivity, higher thermal conductivity, and better anti-electromigration capability. The use scale of copper target material accounts for 15%-25% of the total sputtering target material, and the market demand is large. In the semiconductor field, copper target material is mainly used as an interconnection material for integrated circuits with a technology node of 90-7 nm. It can not only reduce delay and improve operation efficiency, but also improve the reliability of integrated circuits. As target materials continue to develop in the direction of large size, high purity, and high sputtering rate, and chips continue to develop towards smaller technology nodes and centralization, the requirements for the purity, organizational uniformity, crystal orientation, and thermal stability of copper target material are higher.

[0004] Patent CN11113857402B discloses a preparation method of alloy high-purity copper target material. The copper blank is sequentially subjected to one-time forging stretching + one-time heat treatment, two-time forging stretching + two-time heat treatment, three-time forging stretching + four-time forging stretching + static pressure + rolling + four-time heat treatment. The use of multiple forging and heat treatment can achieve the refinement of the organization to a certain extent. However, uneven stress is easy to occur during rolling in the process, which makes it difficult to guarantee the uniformity of the target blank organization, and the preparation cycle is long and complicated.

[0005] Patent CN114892135B discloses a high-purity copper target material and a preparation method and application thereof. The high-purity copper ingot is sequentially subjected to one-time hot forging + one-time heat treatment, two-time hot forging + two-time heat treatment, static pressure + cold rolling treatment to obtain a copper target blank in an unannealed state. The operation is simple and easy for industrial production, and the organizational uniformity is high. However, the biggest problem is that the organizational stability is poor during sputtering use, which is easy to cause recovery and recrystallization, and even target material deformation, which seriously affects the quality of sputtering film coating and the service life of the target material.

[0006] Patent CN103173729B discloses a method for manufacturing copper target material for sputtering, which controls the crystal orientation by casting, hot rolling and cold rolling of oxygen-free copper with a purity of 3N or more, so as to improve the sputtering plating rate and the plating quality to a certain extent. Similarly, the target material prepared by the method has poor stability of unannealed structure, which is not conducive to the quality of sputtering plating. SUMMARY

[0007] The technical problem to be solved by the present application is to provide a preparation method of high-homogeneity and high-stability copper target material to solve the problems of the prior art.

[0008] To solve the above technical problems, the technical scheme adopted by the present application is as follows: a preparation method of high-homogeneity and high-stability copper target material, characterized in that the method comprises the following steps of pretreatment, forging, room temperature circumferential rolling, double-stage annealing heat treatment, machining and cleaning and packaging.

[0009] Step one, pretreatment: a high-purity copper ingot with a mass purity of 99.9999% or more is cut to remove the riser, then the surface oxide layer is removed by turning, and the turning depth is 2mm or more, to obtain a pretreated high-purity copper ingot;

[0010] Step two, forging: the pretreated high-purity copper ingot obtained in step one is heated and kept in the furnace, then forged, elongated to 200%~320% of the original length, then upset to 30%~50% of the length after elongation, repeated upsetting and drawing at least three times, and finally shaped to obtain a forged copper blank;

[0011] Step three, room temperature circumferential rolling: the forged copper blank obtained in step two is subjected to room temperature circumferential rolling, and the total deformation amount is 30%~60% to obtain a rolled copper blank;

[0012] Step four, double-stage annealing heat treatment: the rolled copper blank obtained in step three is subjected to double-stage annealing heat treatment by heating and keeping in the furnace, and then air-cooled to room temperature to obtain a copper target blank;

[0013] Step five, machining and cleaning package: the copper target blank obtained in step four is machined, straightened, vacuum annealed, cleaned, and packaged to obtain high homogeneity and high stability copper target material.

[0014] The preparation method of the high homogeneity and high stability copper target material has the characteristics that before the heating and holding in step two, a copper alloy deformation glass protective lubricant is uniformly coated on the surface of the pretreated high-purity copper ingot and air dried, the temperature of the heating and holding is 580-850 DEG C, and the holding time is 1-2 hours. By uniformly coating the copper alloy deformation glass protective lubricant on the surface of the pretreated high-purity copper ingot, the temperature drop in the forging process is obviously slowed down, the glass protective lubricant can also disperse the deformation process, avoid the cracking of the blank, improve the deformation ability of the high-purity copper ingot, and further improve the production efficiency; by controlling the temperature and holding time of the heating and holding, the high-purity copper ingot has good deformation ability, and the temperature is not too high to cause grain coarsening and abnormal growth, which is beneficial to ensuring the uniformity of the product copper target material.

[0015] The preparation method of the high homogeneity and high stability copper target material has the characteristics that in step three, the downward displacement of each pass of the room temperature circumferential rolling treatment is 1-2 mm, and the included angle of the rolling directions of adjacent passes is 60-120 DEG. By controlling the process parameters of the room temperature circumferential rolling treatment, the deformation unevenness of the surface layer and the core of the copper blank caused by the conventional unidirectional rolling is effectively avoided, the formation of the strong texture and the gradient structure in the annealing process is weakened, and the uniformity of the copper target material is improved.

[0016] The preparation method of the high homogeneity and high stability copper target material has the characteristics that in step four, the process of the double-stage annealing heat treatment is: first, heating to 500-600 DEG C and holding for 10-40 minutes, then heating to 350-450 DEG C and holding for 1-3 hours, and air cooling to room temperature. The double-stage annealing heat treatment is adopted, that is, first, heating to high temperature and holding for a short time to effectively improve the nucleation rate of recrystallization, and then heating to low temperature and holding for a long time to avoid the excessive growth of the recrystallized grains, so that the nucleation rate and the growth rate of the grains are controlled to effectively refine the structure and improve the uniformity of the structure.

[0017] The preparation method of the high homogeneity and high stability copper target material has the characteristics that in step five, the average grain size of the high homogeneity and high stability copper target material is not more than 30 μm, the maximum grain size is not more than 50 μm, the orientation rate of the closest packed {111} plane is more than 55%, and the grain size and the crystal orientation of the transverse and longitudinal structures show excellent uniformity. The grain size and the crystal orientation distribution of the copper target material prepared by the method show high uniformity, which is suitable for being used as a high-quality semiconductor thin film sputtering target material.

[0018] Generally, the microstructure of the copper target material is observed by an optical microscope to analyze the uniformity of the microstructure and the grain size range; and the crystal orientation of different positions is detected and analyzed by an X-ray diffractometer. The orientation rate of the {111} plane is that the sum of the intensities of the {111} plane, the {200} plane, the {220} plane, the {311} plane and the {222} plane in the measured X-ray diffraction data is 100%, and the percentage of the intensity of the {111} plane in the total intensity is the orientation rate of the {111} plane.

[0019] In addition, the sputtering target material has a significant temperature rise during high-power sputtering, even if circulating cooling water is provided on the back plate of the sputtering target material. Currently, sputtering is developing towards high power. In actual operation, the temperature of the outermost surface of the sputtering target material is about 700 DEG C, and the temperature near the surface can reach 500 DEG C. The prepared copper target material is heated and kept at 500 DEG C in the present application to verify the thermal stability of the microstructure.

[0020] Compared with the prior art, the present application has the following advantages:

[0021] 1. The present application significantly weakens the uneven stress distribution of the single-direction rolling deformation by the room temperature circumferential rolling combined with the double-stage annealing heat treatment process, avoids the gradient distribution of the surface layer and the internal layer and the abnormal growth of the grains in the longitudinal microstructure of the copper target material, improves the uniformity of the microstructure from the surface layer to the core of the copper target material, and reduces the loss of the machining of the target blank, which is beneficial to improve the utilization rate of the target blank, save raw materials and reduce costs.

[0022] 2. The present application effectively controls the grain nucleation rate and growth rate of the rolled copper blank by the process design of the double-stage annealing heat treatment, thereby refining the microstructure and avoiding excessive growth of the microstructure, and improving the overall microstructure uniformity of the annealed copper target blank, which is beneficial to ensure the stability and uniformity of the sputtering and plating film of the copper target material.

[0023] 3. The present application realizes good control of the crystal orientation of the copper target material by the process design of the room temperature circumferential rolling combined with the double-stage annealing heat treatment, and the orientation rate of the closest-packed {111} plane is more than 55%, thereby improving the sputtering and plating rate of the copper target material and the uniformity of the film layer.

[0024] 4. The present application improves the thermal stability of the entire copper target material microstructure by changing the stress distribution state and recrystallization behavior of the copper target material by the process design of the room temperature circumferential rolling combined with the double-stage annealing heat treatment, and thereby improves the stability and quality of the sputtering and plating film.

[0025] The technical solutions of the present application are described in further detail below by means of the accompanying drawings and examples. BRIEF DESCRIPTION OF DRAWINGS

[0026] Figure 1Metallographic structure diagram of copper target material prepared for the present embodiment 1.

[0027] Figure 2 Average grain size distribution diagram of longitudinal organization of copper target material prepared for the present embodiment 1 and comparative example 1.

[0028] Figure 3 Distribution diagram of closest packed plane orientation rate of longitudinal organization of copper target material prepared for the present embodiment 1 and comparative example 1.

[0029] Figure 4 Metallographic structure diagram of copper target material prepared for the present embodiment 1 and comparative example 1 at 500℃ for 2h. DETAILED DESCRIPTION

[0030] Embodiment 1

[0031] The present embodiment comprises the following steps:

[0032] Step one, pretreatment: cut off the riser of high purity copper ingot with mass purity of 99.9999% or above, then clean after removing the surface oxidation layer by turning, and the turning depth is 2mm, to obtain pretreated high purity copper ingot;

[0033] Step two, forging: uniformly coat the surface of the pretreated high purity copper ingot obtained in step one with copper alloy deformation glass protective lubricant and air dry, then heat up to 850℃ with the furnace and keep for 1h, then perform forging, first elongate to 200% of the original length, then upset to 30% of the length after elongation, repeat upsetting and drawing treatment three times, and finally shape, to obtain a diameter of 120mm of forged copper bar stock;

[0034] Step three, room temperature circumferential rolling: cut the forged copper bar stock obtained in step two to a height of 20mm, perform room temperature circumferential rolling treatment, the down pressure of each pass is 1mm, and the included angle of the rolling direction of adjacent passes is 60°, and the total deformation amount of rolling is 50%, to obtain rolled copper stock;

[0035] Step four, double-stage annealing heat treatment: first heat the rolled copper stock obtained in step three to 500℃ and keep for 30min, then cool to room temperature in air, then heat to 400℃ and keep for 3h, and cool to room temperature in air, to obtain copper target material stock;

[0036] Step five, machining, cleaning and packaging: perform machining, straightening, vacuum annealing, cleaning treatment and packaging on the copper target material stock obtained in step four, to obtain high homogenization and high stability copper target material with a diameter x thickness of 180mm x 9mm.

[0037] Figure 1 Metallographic structure diagram of copper target material prepared for the present embodiment, from Figure 1It can be seen that the microstructure of the copper target material is in a completely recrystallized state, the grains are fine, the grain size distribution is uniform, and there is no abnormal growth.

[0038] Comparative Example 1

[0039] The present comparative example comprises the following steps:

[0040] Step one, pretreatment: a high-purity copper ingot with a mass purity of 99.9999% or more is cut to remove the riser, then the surface oxide layer is removed by turning, and the turning depth is 2mm, and the pretreated high-purity copper ingot is cleaned;

[0041] Step two, forging: the surface of the pretreated high-purity copper ingot obtained in step one is uniformly coated with a copper alloy deformation glass protective lubricant and air dried, then heated to 850℃ in the furnace for 1h, and then forged, first elongated to 200% of the original length, then upset to 30% of the length after elongation, repeated upsetting and drawing three times, and finally formed into a diameter of 120mm of the forged copper rod blank;

[0042] Step three, room temperature circumferential rolling: the blank with a height of 20mm is cut from the forged copper rod blank obtained in step two, and is subjected to room temperature single-direction rolling treatment, with a downward amount of 1mm per pass, and the rolling direction of adjacent passes remains the same, and the total deformation amount is 50%, to obtain a rolled copper blank;

[0043] Step four, single-stage annealing heat treatment: the rolled copper blank obtained in step three is heated to 500℃ and kept in the furnace for 1h, and then air-cooled to room temperature to obtain a copper target blank;

[0044] Step five, machining, cleaning and packaging: the copper target blank obtained in step four is machined, straightened, vacuum annealed, cleaned and packaged to obtain a copper target material with a diameter x thickness of 180mm x 9mm.

[0045] Figure 2 The average grain size distribution graph of the longitudinal microstructure of the copper target material prepared in Example 1 and Comparative Example 1 of the present application, Figure 3 The most densely packed face orientation rate distribution graph of the longitudinal microstructure of the copper target material prepared in Example 1 and Comparative Example 1 of the present application, Figure 4 The metallographic structure graph of the copper target material prepared in Example 1 and Comparative Example 1 of the present application at 500℃ for 2h, Figure (a) represents Example 1, and Figure (b) represents Comparative Example 1, from Figures 2-4It can be seen that the copper target material prepared in Example 1 has an average grain size of about 28.5 μm, a maximum grain size of about 46 μm, an orientation rate of the closest-packed {111} plane of about 58%, and excellent uniformity in both transverse and longitudinal organizations, including grain size and crystal orientation distribution, and the copper target material grains do not grow significantly after being kept at 500 ℃ for 2 h, thus having excellent thermal stability, so that the copper target material prepared by the method of the present application is suitable as a high-quality sputtering target material for semiconductor thin films; and the copper target material prepared in Comparative Example 1 has an average grain size of about 36 μm, a maximum grain size of 116 μm, and an orientation rate of the closest-packed {111} plane of about 28%, so that the copper target material prepared by the method of the present application has poor uniformity in organization, the grain sizes in the surface layer and the inner portion are gradiently distributed, the closest-packed plane has a low and uneven proportion, and the organization stability is poor, and the copper target material grains grow significantly after being kept at 500 ℃ for 2 h.

[0046] In summary, the present application greatly improves the organization of the copper target material, including grain size and crystal orientation uniformity and stability, by the process of room-temperature circumferential rolling combined with double-stage annealing heat treatment.

[0047] Example 2

[0048] This example includes the following steps:

[0049] Step 1, pretreatment: a high-purity copper ingot with a mass purity of more than 99.99999% is cut to remove the sprue, then the surface oxide layer is removed by turning, and the turned ingot is cleaned, and the turning depth is 3 mm, to obtain a pretreated high-purity copper ingot;

[0050] Step 2, forging: the pretreated high-purity copper ingot obtained in Step 1 is uniformly coated with a copper alloy deformation glass protective lubricant and air-dried, then heated to 580 ℃ in the furnace and kept for 2 h, and then forged, first elongated to 320% of the original length, then upset to 50% of the length after elongation, repeated upsetting and drawing four times, and finally shaped, to obtain a forged copper plate blank with a length × width × thickness of 450 mm × 330 mm × 50 mm;

[0051] Step 3, room-temperature circumferential rolling: the forged copper plate blank obtained in Step 2 is subjected to room-temperature circumferential rolling, with a reduction of 2 mm per pass, and the included angle between the rolling directions of adjacent passes is 90°, and the total deformation is 60%, to obtain a rolled copper blank;

[0052] Step 4, double-stage annealing heat treatment: the rolled copper blank obtained in Step 3 is first heated to 600 ℃ and kept for 10 min, then cooled to room temperature, then heated to 450 ℃ and kept for 1 h, and then cooled to room temperature, to obtain a copper target material blank;

[0053] Step five, machining and cleaning and packaging: the copper target blank obtained in step four is machined, straightened, vacuum annealed, cleaned and packaged to obtain high homogeneity and high stability copper target material with length x width x thickness of 500 mm x 100 mm x 10 mm.

[0054] It is detected that the average grain size of the copper target material prepared in the embodiment is about 20.5 μm, the maximum grain size is about 36 μm, the orientation rate of the closest-packed {111} plane is about 56%, and the transverse and longitudinal organizations exhibit excellent uniformity, not only including the grain size, but also the crystal orientation distribution exhibits high uniformity, and the copper target grain does not significantly grow after being kept at 500 ℃ for 2 h, and has excellent thermal stability, so the copper target material prepared by the method of the embodiment is suitable as a high-quality semiconductor thin film sputtering target material.

[0055] Example 3

[0056] The embodiment includes the following steps:

[0057] Step one, pretreatment: a high-purity copper ingot with a mass purity of 99.99996% is cut to remove the riser, and then cleaned after turning to remove the surface oxide layer, and the turning depth is 2.4 mm, to obtain a pretreated high-purity copper ingot;

[0058] Step two, forging: the surface of the pretreated high-purity copper ingot obtained in step one is uniformly coated with a glass protective lubricant for copper alloy deformation and air dried, then heated to 650 ℃ in the furnace for 2 h, and then forged, first elongated to 320% of the original length, then upset to 30% of the length after elongation, repeated upsetting and drawing four times, and finally formed to obtain a forged copper rod blank with a diameter of 140 mm;

[0059] Step three, room temperature circumferential rolling: the blank with a height of 50 mm is cut from the forged copper rod blank obtained in step two, and subjected to room temperature circumferential rolling treatment, with a downward amount of 1 mm per pass, and an included angle of 120° between adjacent pass directions, and a total deformation of 30%, to obtain a rolled copper blank;

[0060] Step four, double-stage annealing heat treatment: the rolled copper blank obtained in step three is first heated to 500 ℃ in the furnace for 40 min, and then cooled to room temperature, and then heated to 350 ℃ in the furnace for 3 h, and then cooled to room temperature, to obtain a copper target blank;

[0061] Step five, machining and cleaning and packaging: the copper target blank obtained in step four is machined, straightened, vacuum annealed, cleaned and packaged to obtain high homogeneity and high stability copper target material with length x width x thickness of 500 mm x 100 mm x 10 mm.

[0062] The average grain size of the copper target prepared in the embodiment is about 24 μm, the maximum grain size is about 46.5 μm, the orientation rate of the closest-packed {111} plane is about 57%, and the transverse and longitudinal organizations show excellent uniformity, including not only the grain size, but also the crystal orientation distribution, the copper target grain does not grow obviously after being kept at 500 ℃ for 2 h, and has excellent thermal stability, so the copper target prepared by the method of the embodiment is suitable as a high-quality semiconductor thin film sputtering target

[0063] The above merely describes preferred embodiments of the present application, and is not intended to limit the present application. Any simple modification, change and equivalent variation of the above embodiments according to the technical essence of the present application are still within the protection scope of the technical scheme of the present application.

Claims

1. A method for preparing a high homogeneity and high stability copper target material, characterized in that, The method comprises pretreatment, forging, room temperature circumferential rolling, two-stage annealing heat treatment, machining and cleaning and packaging, and the specific steps are as follows: Step one, pretreatment: a high-purity copper ingot with a mass purity of more than 99.9999% is cut to remove the riser, then the surface oxide layer is removed by turning, and the turning depth is more than 2 mm, to obtain a pretreated high-purity copper ingot; Step two, forging: the pretreated high-purity copper ingot obtained in step one is heated and kept in the furnace, then forged, first elongated to 200%~320% of the original length, then upset to 30%~50% of the length after elongation, repeated upsetting and drawing at least three times, and finally formed to obtain a forged copper blank; the heating and keeping temperature is 580℃~850℃, and the keeping time is 1h~2h; Step three, room temperature circumferential rolling: the forged copper blank obtained in step two is subjected to room temperature circumferential rolling treatment, and the total deformation amount is 30%~60% to obtain a rolled copper blank; the downward amount of each pass of the room temperature circumferential rolling treatment is 1mm~2mm, and the included angle of the rolling direction of adjacent passes is 60°~120°; Step four, two-stage annealing heat treatment: the rolled copper blank obtained in step three is subjected to two-stage annealing heat treatment of heating and keeping in the furnace, and then air-cooled to room temperature to obtain a copper target material blank; the two-stage annealing heat treatment process is: first heating to 500℃~600℃ and keeping in the furnace for 10min~40min, then heating to 350℃~450℃ and keeping in the furnace for 1h~3h, and air-cooled to room temperature; Step five, machining, straightening, vacuum annealing, cleaning and packaging: the copper target material blank obtained in step four is subjected to machining, straightening, vacuum annealing, cleaning and packaging to obtain a high-homogeneity and high-stability copper target material.

2. The method of claim 1, wherein the high homogeneity and high stability copper target is prepared by the steps of: Before the heating and keeping in step two, the surface of the pretreated high-purity copper ingot is uniformly coated with a copper alloy deformation glass protective lubricant and dried. ​ 3. The method of claim 1, wherein the high homogeneity and high stability copper target is prepared by the steps of: In step five, the average grain size of the high-homogeneity and high-stability copper target material is not more than 30μm, the maximum grain size is not more than 50μm, the orientation rate of the closest packed {111} plane is more than 55%, and the grain size and crystal orientation of the transverse and longitudinal structures both exhibit excellent uniformity. ​

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