A ring-shaped high-purity copper-phosphorus anode for integrated circuits and its preparation method

Abstract

The present invention relates to the technical field of electroplating equipment, and particularly relates to a ring-shaped high-purity copper-phosphorus anode for integrated circuits and a preparation method thereof. The preparation method of the present invention first obtains a copper-phosphorus ingot by melting, then performs homogenization heat treatment on the ingot, then obtains a tube blank by reverse extrusion deformation, then performs low-temperature stress relief annealing treatment on the tube blank, and finally cuts, machined into shape, cleans, dries and packages the tube blank to obtain a ring-shaped high-purity copper-phosphorus anode. The preparation method of the present invention controls the grain size and the degree of compositional uniformity by performing homogenization treatment on the ingot, adjusting the extrusion temperature and the extrusion ratio, and performing low-temperature annealing treatment. At the same time, multiple copper-phosphorus target blanks can be obtained at one time by cutting on the copper-phosphorus alloy tube. This preparation method can ensure uniform grain distribution, avoid segregation of P elements, eliminate the residual stress of the material, prevent deformation and cracking of the subsequent processed blank, and at the same time, this method can significantly shorten the process flow, improve production efficiency, and reduce production costs.

Description

Technical Field

[0001] The present invention relates to the field of electroplating technology, and particularly relates to a ring-shaped high-purity copper-phosphorus anode for integrated circuits and a preparation method thereof. Background Art

[0002] In recent years, the production capacity of integrated circuits with advanced processes of 28 nm and below globally has accounted for an increasingly large proportion of the total chip manufacturing production capacity. The reduction of feature size has made ultra-high-purity copper and its alloys become increasingly important interconnect materials in the manufacturing process. They are used for interconnecting components within chips in front-end wafer manufacturing and for high-density packaging integration interconnects between chips in back-end advanced packaging. The interconnect process is realized by PVD sputtering or ECP electroplating processes. Interconnect materials such as ultra-high-purity copper and its alloy targets and anodes have advantages in terms of low resistivity, high resistance to electromigration, lower cost, higher wiring density, and narrower wiring width, etc., and are increasingly widely used in the field of high-end integrated circuits. The market demand continues to grow, and they have become the main raw materials for preparing various electronic components in current integrated circuits. Among them, ultra-high-purity copper and its alloy targets are mainly applied to magnetron sputtering, and the prepared interconnect thin film materials have advantages such as high purity, excellent conductivity, and good aspect ratio coverage. The copper-phosphorus anode is mainly applied to electroplating, which can achieve low-temperature and high-efficiency deposition and is used to fill the through-hole interconnect structure. The P element in the copper-phosphorus anode can react with Cu + to form a black film, which can accelerate the oxidation of Cu + and reduce the accumulation of Cu + and can also reduce the shedding of small grains from the anode, prevent the copper anode from dissolving too quickly, improve the anode utilization rate, and make the components more stable to a certain extent.

[0003] Currently, copper-phosphorus anodes are mainly prepared by methods of multiple plastic deformation processing and heat treatment. For example, Chinese Patent CN102517621B discloses a preparation method of a copper-phosphorus alloy anode. The preparation method includes the following steps: heating a copper-phosphorus ingot and then forging it, repeatedly heating and forging three rounds, cooling, then performing a second heat treatment, then cold-rolling the blank and performing a third heat treatment, and finally machining the blank to obtain a copper-phosphorus anode. The copper-phosphorus anode prepared by this method can meet the electroplating requirements, but has disadvantages such as complicated production processes, low automation degree, long processing cycle, low production efficiency, and high cost. Summary of the Invention

[0004] Based on the problems existing in the prior art, the present invention provides a ring-shaped high-purity copper-phosphorus anode for integrated circuits and a preparation method thereof. The specific technical solutions are as follows:

[0005] A preparation method of a ring-shaped high-purity copper-phosphorus anode for integrated circuits includes the following steps:

[0006] Step 1: Obtain a copper - phosphorus melt through smelting, and subject the copper - phosphorus melt to static - mold casting under a vacuum state to obtain a cylindrical ingot;

[0007] Step 2: Conduct homogenization heat treatment on the cylindrical ingot. The homogenization heat treatment temperature is 600 - 700 °C, and the time is 6 - 8 h to obtain a homogenized ingot;

[0008] Step 3: Conduct backward extrusion deformation on the homogenized ingot. During the extrusion deformation process, the material temperature is 550 - 700 °C, and it is lower than the homogenization heat treatment temperature. The extrusion speed is 6 - 8 mm / s, and the extrusion ratio is 1.5 - 4.5 to obtain a high - purity copper - phosphorus tube blank;

[0009] Step 4: Anneal the high - purity copper - phosphorus tube blank. The annealing temperature is 200 - 300 °C, and the annealing time is 1 - 2 h;

[0010] Step 5: Cut the high - purity copper - phosphorus tube blank annealed in Step 4, and then use a high - precision numerical control machine tool for machining and forming to obtain a ring - shaped high - purity copper - phosphorus anode for integrated circuits, where the machining accuracy of the high - precision numerical control machine tool is ±0.01 mm.

[0011] Further, in Step 1, a vacuum induction melting or magnetic levitation melting is used to obtain the copper - phosphorus melt.

[0012] Further, in Step 1, the casting temperature for static - mold casting is 1100 - 1200 °C, and the casting time is 4 - 5 min.

[0013] Further, the purity of the cylindrical ingot obtained in Step 1 is 99.9% - 99.999%, the P content is 400 - 650 ppm, and the diameter is 150 - 200 mm.

[0014] Further, during the homogenization heat treatment in Step 2, the furnace temperature fluctuation does not exceed ±5 °C.

[0015] Further, the wall thickness of the high - purity copper - phosphorus tube blank obtained in Step 3 is 10 - 40 mm.

[0016] Further, the cutting method in Step 5 is high - speed wire - saw cutting, and the cutting accuracy is 0.2 mm.

[0017] Further, in Step 5, a high - precision numerical control machine tool is used to machine the outer diameter, inner diameter, upper surface, and lower surface of the high - purity copper - phosphorus tube blank to obtain a ring - shaped finished product. The inner diameter of the ring - shaped finished product is 220 - 270 mm, the outer diameter is 270 - 300 mm, the wall thickness is 10 - 40 mm, and the height is 30 - 40 mm.

[0018] Further, the obtained annular high-purity copper-phosphorus anode for integrated circuits in step 5 is further cleaned, vacuum dried, and plastic-sealed.

[0019] An annular high-purity copper-phosphorus anode for integrated circuits prepared according to the above preparation method has a grain size of 100 - 300 μm.

[0020] The beneficial effects of the present invention are as follows:

[0021] (1) For the preparation method of an annular high-purity copper-phosphorus anode for integrated circuits provided by the present invention, compared with the traditional preparation method of multiple plastic deformations + heat treatment of a single-piece target blank, the method of the present invention directly prepares copper-phosphorus alloy tubes through a one-step hot extrusion forming technique, and obtains multiple copper-phosphorus tube blanks at one time through wire saw cutting, solving the disadvantages of the traditional preparation method such as complicated production processes, long processing cycles, low production efficiency, and high costs, and can increase the production efficiency by more than 50%.

[0022] (2) For the preparation method of an annular high-purity copper-phosphorus anode for integrated circuits provided by the present invention, in the preparation of the high-purity copper-phosphorus ingot involved, a vacuum induction melting or magnetic levitation melting method is adopted, combined with a static mold casting method under a vacuum state. By controlling the pouring temperature and time and the pouring speed, a cylindrical ingot with a good flat surface, uniform composition distribution, and no internal defects is obtained, and the yield rate can reach more than 95%.

[0023] (3) For the preparation method of an annular high-purity copper-phosphorus anode for integrated circuits provided by the present invention, first, through homogenization heat treatment, the internal chemical composition of the copper-phosphorus ingot is made more uniform, reducing the segregation of P elements and improving the quality stability of the product electroplated film. Subsequently, by adjusting the extrusion temperature and extrusion ratio, the grain size is controlled to obtain uniform and fine equiaxed grains with an average grain size ≤ 250 μm, avoiding the stratification of the internal structure of the copper-phosphorus alloy and improving the uniformity of the product electroplated film. Finally, through a low-temperature annealing process, ensuring that its annealing temperature is lower than the recrystallization temperature of the copper-phosphorus alloy, eliminating residual stress, preventing the blank for subsequent processing from deforming and cracking, and at the same time preventing the internal structure of the copper-phosphorus alloy from recrystallizing and growing. Description of the Drawings

[0024] The following further describes the embodiments of the present invention with reference to the drawings, where:

[0025] Figure 1 is the preparation flow chart of the annular high-purity copper-phosphorus anode for integrated circuits of the present invention;

[0026] Figure 2 is the 50X micrograph of the copper-phosphorus anode blank in Example 1 of the present invention;

[0027] Figure 3This is the 50X microstructural diagram of the copper-phosphorus anode blank in Embodiment 2 of the present invention;

[0028] Figure 4 This is the 50X microstructural diagram of the copper-phosphorus anode blank in Embodiment 3 of the present invention. Detailed implementation manners

[0029] In order to make the objectives, technical solutions and advantages of the present invention clearer and more understandable, the present invention will be further described in detail below through specific embodiments in conjunction with the accompanying drawings. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0030] Embodiment 1

[0031] Manufacture a high-purity annular copper-phosphorus anode with a purity of 4N5, a P content of 525 ppm, and a size of Φ(297 - 270)*38 mm, mainly including the following steps:

[0032] (1) Preparation of high-purity copper-phosphorus ingot: A high-purity copper-phosphorus ingot is obtained by vacuum induction melting and static mold casting. The casting temperature of static mold casting is 1100 °C, the casting time is 5 min, the casting speed is kept uniform and large at 38 kg / min in the early stage of casting, and the flow rate is reduced to 26 kg / min and slowly cast after 2.5 min. After melting, the diameter of the ingot is 200 mm and the length is 580 mm.

[0033] (2) Homogenization heat treatment: The ingot is subjected to homogenization heat treatment. After the furnace temperature reaches the set temperature, the melted ingot, i.e., the cylindrical ingot, is added to the heating furnace. The heating temperature is 700 ± 5 °C. After the temperature returns to normal, timing starts. The heating time is 6.5 h ± 10 min, and the temperature fluctuation at each part of the heat treatment furnace does not exceed ±5 °C. Homogenization heat treatment at this temperature makes the internal chemical composition of the copper-phosphorus ingot more uniform and reduces the segregation of P element.

[0034] (3) Preparation of high-purity copper-phosphorus alloy tube: The ingot is extruded and deformed by a 3000T reverse extrusion machine. The extrusion temperature is controlled at 680 ± 10 °C, the extrusion speed is 7 mm / s, the extrusion ratio is 2.1, and the outer diameter of the copper-phosphorus tube after extrusion is 300 mm and the wall thickness is 17 mm.

[0035] (4) Stress relief annealing: Immediately perform non-vacuum heat treatment on the copper-phosphorus tube after hot extrusion. When the temperature reaches the furnace temperature, start timing after the temperature returns to normal. The heating temperature is 230 ± 10 °C, and the heating time is 1.5 h ± 10 min. The temperature fluctuation at each part of the heat treatment furnace does not exceed ±5 °C. This heat treatment temperature is lower than the recrystallization temperature of the copper-phosphorus alloy. While eliminating the residual stress and preventing the billet from deforming and cracking during subsequent processing, it also prevents the internal structure of the copper-phosphorus alloy from recrystallizing and growing.

[0036] (5) Preparation of high-purity copper-phosphorus target blanks and machining, cleaning, drying, and packaging of copper-phosphorus anodes: The copper-phosphorus alloy tubes are cut into single copper-phosphorus target blanks with a height of 38 ± 1 mm using high-speed abrasive wire cutting. The number of target blanks cut from a single alloy tube is 28. Subsequently, the tube blanks are machined using a CNC milling machine to obtain finished ring-shaped copper-phosphorus anodes. The surface dirt of the finished anodes is removed by cleaning, and then they are dried in a vacuum oven. After cooling, they are vacuum-sealed using a vacuum bag to prevent anodic oxidation.

[0037] Metallographic analysis: Samples are taken from the above blanks for metallographic analysis, and finally, the grain size is 170 μm, as shown in Figure 2 . Example 2

[0038] Manufacture of high-purity ring-shaped copper-phosphorus anodes with a purity of 4N, a P content of 450 ppm, and a size of Φ(285 - 265)*35 mm, mainly including the following steps:

[0039] (1) Preparation of high-purity copper-phosphorus ingots: High-purity copper-phosphorus ingots are obtained by vacuum induction melting and static mold casting. The casting temperature for static mold casting is 1150 °C, the casting time is 5 min, the pouring speed is maintained at a uniform and large flow rate of 40 kg / min in the early stage of pouring, and the flow rate is reduced to 20 kg / min for slow pouring after 3 min. After melting, the diameter of the ingot is 200 mm and the length is 580 mm.

[0040] (2) Homogenization heat treatment: The ingots are subjected to homogenization heat treatment. After the furnace temperature reaches the set temperature, the melted ingots, i.e., cylindrical ingots, are added to the heating furnace. The heating temperature is 680 ± 10 °C. After the temperature returns to the set value, the timing starts. The heating time is 7 h ± 10 min, and the temperature fluctuation in each part of the heat treatment furnace does not exceed ±5 °C.

[0041] (3) Preparation of high-purity copper-phosphorus alloy tubes: The ingots are extruded and deformed using a 3000T reverse extrusion machine. The extrusion temperature is controlled at 630 ± 10 °C, the extrusion speed is 6 mm / s, and the extrusion ratio is 2.8. After extrusion, the outer diameter of the copper-phosphorus tubes is 288 mm and the wall thickness is 13 mm.

[0042] (4) Stress relief annealing: The hot-extruded copper-phosphorus tubes are immediately subjected to non-vacuum heat treatment. When the temperature reaches the set value, they are put into the furnace, and the timing starts after the temperature returns to the set value. The heating temperature is 280 ± 10 °C, and the heating time is 1.2 h ± 10 min. The temperature fluctuation in each part of the heat treatment furnace does not exceed ±5 °C.

[0043] (5) Preparation of high-purity copper-phosphorus target blanks and machining, cleaning, drying, and packaging of copper-phosphorus anodes: Cut copper-phosphorus alloy tubes into single copper-phosphorus target blanks with a height of 39 ± 1 mm using high-speed abrasive wire cutting. The number of target blanks cut from a single alloy tube is 40. Subsequently, use a CNC milling machine to machine the tube blanks to obtain finished ring-shaped copper-phosphorus anodes. Clean the surface dirt of the finished anodes, then place them in a vacuum oven for drying, and after cooling, use a vacuum bag for vacuum sealing to prevent anode oxidation.

[0044] Metallographic analysis: Take samples from the above billets for metallographic analysis, and finally obtain a grain size of 120 μm, as shown in Figure 3 . Example 3

[0045] Manufacture high-purity ring-shaped copper-phosphorus anodes with a purity of 3N5, a P content of 600 ppm, and a size of Φ(276 - 240)*30 mm, mainly including the following steps:

[0046] (1) Preparation of high-purity copper-phosphorus ingots: Obtain high-purity copper-phosphorus ingots using vacuum induction melting and static mold casting. The casting temperature for static mold casting is 1200 °C, the casting time is 4 min, the pouring speed is maintained at a uniform and large flow rate of 40 kg / min in the early stage of pouring, and after 2.5 min, the flow rate is reduced to 20 kg / min for slow pouring. The diameter of the ingot after melting is 180 mm, and the length is 580 mm.

[0047] (2) Homogenization heat treatment: Conduct homogenization heat treatment on the ingots. After the furnace temperature reaches the set temperature, add the melted ingots, i.e., cylindrical ingots, into the heating furnace. The heating temperature is 650 ± 10 °C. Start timing after the temperature returns. The heating time is 7.5 h ± 10 min, and the temperature fluctuation in each part of the heat treatment furnace does not exceed ±5 °C.

[0048] (3) Preparation of high-purity copper-phosphorus alloy tubes: Use a 3000T reverse extrusion machine to extrude and deform the ingots. Control the extrusion temperature at 630 ± 10 °C, the extrusion speed at 8 mm / s, and the extrusion ratio at 1.5. The outer diameter of the copper-phosphorus tubes after extrusion is 279 mm, and the wall thickness is 21 mm.

[0049] (4) Stress relief annealing: Immediately conduct non-vacuum heat treatment on the hot-extruded copper-phosphorus tubes. Put them into the furnace when reaching the temperature, start timing after the temperature returns. The heating temperature is 290 ± 10 °C, and the heating time is 1.2 h ± 10 min. The temperature fluctuation in each part of the heat treatment furnace does not exceed ±5 °C.

[0050] (5)Preparation of high-purity copper-phosphorus target blanks and machining, cleaning, drying, and packaging of copper-phosphorus anodes: The copper-phosphorus alloy tube is cut into single copper-phosphorus target blanks with a height of 35 ± 1 mm using high-speed abrasive wire cutting. Then, the target blanks are cut into 1 / 4-ring target blanks using water cutting. After cutting a single alloy tube, the number of target blanks is 24 * 4 = 96 pieces. Subsequently, the tube blanks are machined using a CNC milling machine to obtain finished 1 / 4-ring copper-phosphorus anodes. The surface dirt of the finished anodes is removed by cleaning, and then they are dried in a vacuum oven. After cooling, they are vacuum-sealed using a vacuum bag to prevent anode oxidation.

[0051] Metallographic analysis: Samples are taken from the above-mentioned blanks for metallographic analysis, and finally, the grain size is 250 μm, as shown in Figure 4 .

[0052] Some exemplary embodiments of the present invention have been described above. It can be understood that the above embodiments are only used to explain the present invention and do not constitute a limitation to the protection scope of the present invention. The features in these embodiments can be recombined in a suitable manner, and the solutions obtained thereby are still within the protection scope required by the present invention. Based on the above embodiments, all other embodiments obtained by those skilled in the art without creative efforts, that is, all modifications, equivalent replacements, and improvements made within the spirit and principle of this application, fall within the protection scope required by the present invention.

Claims

1. A preparation method of a ring-shaped high-purity copper-phosphorus anode for integrated circuits, characterized in that, It includes the following steps: Step 1: Obtain a copper-phosphorus melt through smelting. Subject the copper-phosphorus melt to static mold casting under a vacuum state to obtain a cylindrical ingot. The casting temperature for static mold casting is 1100 - 1200 °C, and the casting time is 4 - 5 min; Step 2: Conduct homogenization heat treatment on the cylindrical ingot. The homogenization heat treatment temperature is 600 - 700 °C. During the homogenization heat treatment process, the furnace temperature fluctuation does not exceed ±5 °C, and the time is 6 - 8 h to obtain a homogenized ingot; Step 3: Conduct backward extrusion deformation on the homogenized ingot. During the extrusion deformation process, the material temperature is 550 - 700 °C and is lower than the homogenization heat treatment temperature. The extrusion speed is 6 - 8 mm / s, and the extrusion ratio is 1.5 - 4.5 to obtain a high-purity copper-phosphorus tube blank; Step 4: Anneal the high-purity copper-phosphorus tube blank. The annealing temperature is 200 - 300 °C, and the annealing time is 1 - 2 h; Step 5: Cut the high-purity copper-phosphorus tube blank annealed in Step 4, and then use a high-precision numerical control machine tool for machining and forming to obtain a ring-shaped high-purity copper-phosphorus anode for integrated circuits, where the machining accuracy of the high-precision numerical control machine tool is ±0.01 mm.

2. The preparation method of a circular high-purity copper-phosphorus anode for an integrated circuit according to claim 1, characterized in that, In Step 1, a vacuum induction melting or magnetic levitation melting is used to obtain the copper-phosphorus melt.

3. The preparation method of a ring-shaped high-purity copper-phosphorus anode for an integrated circuit according to claim 1, characterized in that, The purity of the cylindrical ingot obtained in Step 1 is 99.9% - 99.999%, the P content is 400 - 650 ppm, and the diameter is 150 - 200 mm.

4. The preparation method of a ring-shaped high-purity copper-phosphorus anode for an integrated circuit according to claim 1, characterized in that, The wall thickness of the tube of the high-purity copper-phosphorus tube blank obtained in Step 3 is 10 - 40 mm.

5. The preparation method of a ring-shaped high-purity copper-phosphorus anode for an integrated circuit according to claim 1, wherein, The cutting method in Step 5 is high-speed wire saw cutting, and the cutting accuracy is 0.2 mm.

6. The preparation method of a ring-shaped high-purity copper-phosphorus anode for an integrated circuit according to claim 1, characterized in that, In Step 5, the high-precision numerical control machine tool is used to machine the outer diameter, inner diameter, upper surface, and lower surface of the high-purity copper-phosphorus tube blank to obtain a ring-shaped finished product. The inner diameter of the ring-shaped finished product is 220 - 270 mm, the outer diameter is 270 - 300 mm, the wall thickness is 10 - 40 mm, and the height is 30 - 40 mm.

7. The preparation method of a ring-shaped high-purity copper phosphorus anode for an integrated circuit according to claim 1, characterized in that, The ring-shaped high-purity copper-phosphorus anode for integrated circuits obtained in Step 5 is further cleaned, vacuum dried, and plastic-sealed and packaged.

8. A ring-shaped high-purity copper-phosphorus anode for integrated circuits prepared by the preparation method according to any one of claims 1-7, characterized in that, Its grain size is 100 - 300 μm.

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