Electroplating method of wafer-level copper cylinder

Abstract

The invention belongs to the field of semiconductors, and particularly discloses an electroplating method for a wafer-level copper cylinder. In the copper cylinder electroplating process, polyvinylpyrrolidone and alkylbenzene sulfonate in the electroplating liquid cooperate with each other, the number of defects such as holes and cracks in the copper cylinder can be obviously reduced, the adhesive force of the copper cylinder is improved, and the mechanical property of the copper cylinder is improved.

Description

Technical Field

[0001] The invention belongs to the field of semiconductors, and in particular relates to an electroplating method for wafer-level copper pillars. Background Art

[0002] Copper pillar bump interconnection technology is one of the key technologies for advanced packaging flip chips and has received widespread attention. The preparation process of copper pillar bumps mainly includes spin coating photoresist (such as polyimide) on silicon wafers and photoresist etching patterning, sputtering seed layer (including Ti or TiW adhesion layer and Cu electroplating seed layer on the adhesion layer, UBM), coating photoresist (PR) and photolithography of the pattern to be electroplated, electroplating of copper pillar bumps, electroplating of solder, removal of PR and UBM, and solder reflow. If it is applied to the chip packaging process of copper-copper bonding, after electroplating the copper pillar, the electroplating of solder is omitted, and the hot pressing bonding process is directly removed after the PR and UBM are removed. In the copper pillar bump interconnection process, electroplating copper pillars is one of the most challenging links. For the reliability of subsequent interconnection, copper pillars are generally required to have a certain mechanical strength to avoid subsequent short circuits caused by defects such as shedding, breakage, and deformation of copper pillars. However, due to the complexity of the electrochemical reaction and microscopic reaction of the electroplating system during the preparation of the electroplated copper pillar, there are often defects such as holes, cracks, and grain coarsening in the deposited copper plating layer, resulting in poor mechanical properties of the copper pillar, affecting the reliability of the copper pillar bump.

[0003] Therefore, there is still a need to continue to develop a technology to improve the mechanical properties of copper pillars. Summary of the invention

[0004] In view of the problem of poor mechanical properties of electroplated copper pillars in the above-mentioned prior art, the present invention provides a method for electroplating wafer-level copper pillars.

[0005] To achieve the above purpose, the following technical solutions are specifically included: A method for electroplating a wafer-level copper column comprises the following steps: (1) Providing chip wafer metal pads to be electroplated; (2) subjecting the metal pads of the chip wafer to be electroplated to air plasma cleaning and acid immersion in sequence; (3) electroplating the metal pads of the chip wafer to be electroplated after acid immersion in step (2) in an electroplating solution, and then cleaning and debonding to obtain the copper pillars; The electroplating solution includes the following components: 100-300 g / L copper sulfate, 40-100 g / L sulfuric acid, Cl - 30-60mg / L, accelerator 25-60mg / L, polyethylene glycol 10-80mg / L, polyvinyl pyrrolidone 10-70mg / L, alkyl benzene sulfonate 10-50mg / L, and the balance water.

[0006] In the process of electroplating copper pillars, polyvinyl pyrrolidone and alkylbenzene sulfonate in the electroplating solution cooperate with each other, which can significantly reduce the number of defects such as holes and cracks in the copper pillars, increase the adhesion of the copper pillars, and improve the mechanical properties of the copper pillars.

[0007] Preferably, the mass ratio of polyvinyl pyrrolidone to alkylbenzene sulfonate is (0.5-6):1.

[0008] Further preferably, the mass ratio of polyvinyl pyrrolidone to alkylbenzene sulfonate is (1-3):1.

[0009] Polyvinyl pyrrolidone is a type of N-vinyl amide polymer, which has adsorption, complexation or polarization effects. The sulfonic group in alkylbenzene sulfonate has a complexation effect. The alkylbenzene sulfonate exists as an anion with strong adsorption and can be used as a surfactant. In the electroplating solution system of the present invention, polyvinyl pyrrolidone and alkylbenzene sulfonate may have a regulatory effect on copper deposition, and together with the inhibitor and accelerator in the electroplating solution, they regulate the deposition of copper, reduce copper grain defects and internal stress, and make the grains in the copper column small, with fewer defects such as holes and cracks, thereby improving the mechanical properties of the copper column. The mass ratio of polyvinyl pyrrolidone and alkylbenzene sulfonate affects the mechanical properties of the final electroplated copper column. Within the above-mentioned mass ratio range, the mechanical properties of the copper column are better and the defects are fewer.

[0010] Preferably, the alkylbenzene sulfonate includes at least one of undecylbenzene sulfonate, dodecylbenzene sulfonate, tridecylbenzene sulfonate, tetradecylbenzene sulfonate, pentadecylbenzene sulfonate, hexadecylbenzene sulfonate, heptadecylbenzene sulfonate, octadecylbenzene sulfonate and nonadecylbenzene sulfonate. The number of carbon atoms in the alkyl group of the alkylbenzene sulfonate is different, and the molecular structure is different. Preferably, the number of carbon atoms in the alkyl group of the alkylbenzene sulfonate is ≥12, and more preferably, the number of carbon atoms in the alkyl group of the alkylbenzene sulfonate is 12-18.

[0011] Preferably, the number average molecular weight of the polyvinyl pyrrolidone is 3500-40000, more preferably, 10000-24000.

[0012] Preferably, the polyethylene glycol includes at least one of PEG-200, PEG-400, PEG-600, PEG-800, PEG-1000, PEG-2000, PEG-3000, PEG-4000, PEG-6000, PEG-8000, PEG-10000, and PEG-20000.

[0013] As an inhibitor of the electroplating solution, polyethylene glycol is easily adsorbed on the copper surface during the electroplating process. It has a polarizing effect on the copper deposition potential, which can inhibit copper deposition. It also has a wetting effect, improving the electroplating quality and mechanical properties of the copper column.

[0014] Preferably, the accelerator comprises at least one of 3-mercapto-1-propane sulfonate, polydisulfide propane sulfonate, 3-mercapto-ethyl sulfonate, and 3-mercapto-1-ethane sulfonic acid potassium salt.

[0015] The accelerator can accelerate the deposition rate of copper ions in the micropores, reduce the defects of leak plating and plating in the micropores; compete with the inhibitor and other substances for adsorption, and improve the electroplating quality of the copper column.

[0016] Preferably, the metal pad of the chip wafer to be electroplated includes, from bottom to top, a wafer substrate, a metal pad, an insulating layer, a metallization layer, and a photoresist; the metallization layer includes an adhesion layer and a copper seed layer, and the thickness of the copper seed layer is 100-500nm; there are micropores on the photoresist, the micropores are located in the metallization layer, the diameter of the micropores is 50-150μm, the pore spacing between the micropores is 80-200μm, and the thickness of the photoresist is 10-150μm.

[0017] Preferably, the current density of the electroplating is 3-40A / dm 2 The electroplating time is 10-60min.

[0018] More preferably, the current density of the electroplating is 5-20A / dm 2 .

[0019] Preferably, the acid used in the acid leaching is a 20-80 g / L sulfuric acid aqueous solution.

[0020] Preferably, the solvents used in the debonding process are tetramethylammonium hydroxide (TMAH) and dimethyl sulfoxide (DMSO).

[0021] A wafer comprises a wafer substrate, a metal pad, an insulating layer and a metallization layer in sequence, and a copper column made on the metallization layer by the electroplating method of the wafer-level copper column.

[0022] Compared with the prior art, the present invention has the following beneficial effects: in the process of electroplating copper pillars, the polyvinyl pyrrolidone and alkylbenzene sulfonate in the electroplating solution cooperate with each other, which can significantly reduce the number of defects such as holes and cracks in the copper pillars, improve the adhesion of the copper pillars, and improve the mechanical properties of the copper pillars. DETAILED DESCRIPTION

[0023] In order to better illustrate the purpose, technical scheme and advantages of the present invention, the present invention will be further described below through specific examples. The test methods used in the examples and / or comparative examples are conventional methods unless otherwise specified; the materials, reagents, etc. used can be obtained from commercial channels unless otherwise specified.

[0024] Example 1 A copper column electroplating method comprises the following steps: (1) Providing a chip wafer metal pad (commercially available, manufactured by Guangdong Fozhixin Microelectronics Technology Research Co., Ltd.) for electroplating copper pillars, the chip wafer metal pad includes, from bottom to top, a wafer substrate, a metal pad, an insulating layer, a metallization layer, a photoresist, and microholes on the photoresist to expose the metallization layer, so as to facilitate the subsequent electroplating of copper pillars; The thickness of the photoresist is 50 μm, the diameter of the micropores thereon is 80 μm, and the spacing between the micropores is 150 μm; The metallization layer includes an adhesion layer and a Cu seed layer sputtered on the surface of the adhesion layer; wherein the adhesion layer can enhance the adhesion between metals, so that the upper and lower layers are firmly adhered and not easy to peel off, and the Cu seed layer is composed of a 100nm Ti barrier layer and a 300nm copper seed layer sputtered by PVD technology, so that the subsequent copper electroplating process can be realized; (2) Use air plasma to clean the metal pad of the chip wafer for 20 seconds, then immerse it in a 50g / L sulfuric acid solution and remove bubbles by shaking. This can remove impurities and bubbles at the bottom of the micropores and increase the wettability of subsequent electroplating. (3) Place the copper column in a copper column electroplating solution for electroplating at a current density of 10ASD (1ASD = A / dm 2 ), the electroplating time is 40min, the electroplating temperature is 30℃, and the stirring rate during the electroplating process is 30rpm; The components of the electroplating solution are: 200g / L copper sulfate pentahydrate, 80g / L sulfuric acid, Cl - 40mg / L, 3-mercapto-1-propanesulfonic acid (sodium) salt (MPS) 30mg / L, polyethylene glycol 1000 (PEG-1000) 40mg / L, polyvinyl pyrrolidone (PVP-24000, average molecular weight 24000, purchased from Aladdin) 50mg / L, sodium dodecylbenzene sulfonate 20mg / L, solvent water; (4) After electroplating, the substrate is washed with water and then the photoresist is removed with a mixed solution of TMAH and DMSO (mass ratio is 1:1) to expose the deposited copper pillars.

[0025] Example 2 The difference between this embodiment and embodiment 1 is that the polyvinyl pyrrolidone in this embodiment is PVP-3500, and specifically comprises the following steps: (1) Providing a chip wafer metal pad (commercially available, manufactured by Guangdong Fozhixin Microelectronics Technology Research Co., Ltd.) for electroplating copper pillars, the chip wafer metal pad includes, from bottom to top, a wafer substrate, a metal pad, an insulating layer, a metallization layer, a photoresist, and microholes on the photoresist to expose the metallization layer, so as to facilitate the subsequent electroplating of copper pillars; The thickness of the photoresist is 50 μm, the diameter of the micropores thereon is 80 μm, and the spacing between the micropores is 150 μm; The metallization layer includes an adhesion layer and a Cu seed layer sputtered on the surface of the adhesion layer; wherein the adhesion layer can enhance the adhesion between metals, so that the upper and lower layers are firmly adhered and not easy to peel off, and the Cu seed layer is composed of a 100nm Ti barrier layer and a 300nm copper seed layer sputtered by PVD technology, so that the subsequent copper electroplating process can be realized; (2) Use air plasma to clean the metal pad of the chip wafer for 200 minutes, then acid immerse it in 50g / L sulfuric acid solution, and use a swinging method to remove bubbles. The swinging method can remove impurities and bubbles at the bottom of the micropores and increase the wettability of subsequent electroplating; (3) Place the copper column in a copper column electroplating solution for electroplating at a current density of 10ASD (1ASD = A / dm 2 ), the electroplating time is 40min, the electroplating temperature is 30℃, and the stirring rate during the electroplating process is 30rpm; The components of the electroplating solution are: 200g / L copper sulfate pentahydrate, 80g / L sulfuric acid, Cl - 40mg / L, 3-mercapto-1-propanesulfonic acid (sodium) salt (MPS) 30mg / L, polyethylene glycol 1000 (PEG-1000) 40mg / L, PVP-3500 (average molecular weight 3500, purchased from Gongbik New Materials Technology (Shanghai) Co., Ltd.) 50mg / L, sodium dodecylbenzene sulfonate 20mg / L, solvent water; (4) After electroplating, the substrate is washed with water and then the photoresist is removed with a mixed solution of TMAH and DMSO (mass ratio is 1:1) to expose the deposited copper pillars.

[0026] Example 3 The difference between this embodiment and embodiment 1 is that the polyvinyl pyrrolidone in this embodiment is PVP-10100, and specifically comprises the following steps: (1) Providing a chip wafer metal pad (commercially available, manufactured by Guangdong Fozhixin Microelectronics Technology Research Co., Ltd.) for electroplating copper pillars, the chip wafer metal pad includes, from bottom to top, a wafer substrate, a metal pad, an insulating layer, a metallization layer, a photoresist, and microholes on the photoresist to expose the metallization layer, so as to facilitate the subsequent electroplating of copper pillars; The thickness of the photoresist is 50 μm, the diameter of the micropores thereon is 80 μm, and the spacing between the micropores is 150 μm; The metallization layer includes an adhesion layer and a Cu seed layer sputtered on the surface of the adhesion layer; wherein the adhesion layer can enhance the adhesion between metals, so that the upper and lower layers are firmly adhered and not easy to peel off, and the Cu seed layer is composed of a 100nm Ti barrier layer and a 300nm copper seed layer sputtered by PVD technology, so that the subsequent copper electroplating process can be realized; (2) Use air plasma to clean the metal pad of the chip wafer for 20 seconds, then immerse it in a 50g / L sulfuric acid solution and remove bubbles by shaking. This can remove impurities and bubbles at the bottom of the micropores and increase the wettability of subsequent electroplating. (3) Place the copper column in a copper column electroplating solution for electroplating at a current density of 10ASD (1ASD = A / dm 2 ), the electroplating time is 40min, the electroplating temperature is 30℃, and the stirring rate during the electroplating process is 30rpm; The components of the electroplating solution are: 200g / L copper sulfate pentahydrate, 80g / L sulfuric acid, Cl - 40mg / L, 3-mercapto-1-propanesulfonic acid (sodium) salt (MPS) 30mg / L, polyethylene glycol 1000 (PEG-1000) 40mg / L, PVP-10100 (average molecular weight 10100, purchased from Topbike New Materials Technology (Shanghai) Co., Ltd.) 50mg / L, sodium dodecylbenzene sulfonate 20mg / L, solvent water; (4) After electroplating, the substrate is washed with water and then the photoresist is removed with a mixed solution of TMAH and DMSO (mass ratio is 1:1) to expose the deposited copper pillars.

[0027] Example 4 The difference between this embodiment and embodiment 1 is that the polyvinyl pyrrolidone in this embodiment is PVP-37900, and specifically comprises the following steps: (1) Providing a chip wafer metal pad (commercially available, manufactured by Guangdong Fozhixin Microelectronics Technology Research Co., Ltd.) for electroplating copper pillars, the chip wafer metal pad includes, from bottom to top, a wafer substrate, a metal pad, an insulating layer, a metallization layer, a photoresist, and microholes on the photoresist to expose the metallization layer, so as to facilitate the subsequent electroplating of copper pillars; The thickness of the photoresist is 50 μm, the diameter of the micropores thereon is 80 μm, and the spacing between the micropores is 150 μm; The metallization layer includes an adhesion layer and a Cu seed layer sputtered on the surface of the adhesion layer; wherein the adhesion layer can enhance the adhesion between metals, so that the upper and lower layers are firmly adhered and not easy to peel off, and the Cu seed layer is composed of a 100nm Ti barrier layer and a 300nm copper seed layer sputtered by PVD technology, so that the subsequent copper electroplating process can be realized; (2) Use air plasma to clean the metal pad of the chip wafer for 20 seconds, then immerse it in a 50g / L sulfuric acid solution and remove bubbles by shaking. This can remove impurities and bubbles at the bottom of the micropores and increase the wettability of subsequent electroplating. (3) Place the copper column in a copper column electroplating solution for electroplating at a current density of 10ASD (1ASD = A / dm 2 ), the electroplating time is 40min, the electroplating temperature is 30℃, and the stirring rate during the electroplating process is 30rpm; The components of the electroplating solution are: 200g / L copper sulfate pentahydrate, 80g / L sulfuric acid, Cl - 40mg / L, 3-mercapto-1-propanesulfonic acid (sodium) salt (MPS) 30mg / L, polyethylene glycol 1000 (PEG-1000) 40mg / L, PVP-37900 (average molecular weight 37900, purchased from Gongbik New Materials Technology (Shanghai) Co., Ltd.) 50mg / L, sodium dodecylbenzene sulfonate 20mg / L, solvent water; (4) After electroplating, the substrate is washed with water and then the photoresist is removed with a mixed solution of TMAH and DMSO (mass ratio is 1:1) to expose the deposited copper pillars.

[0028] Example 5 The difference between this embodiment and embodiment 1 is that the alkylbenzene sulfonate in this embodiment is sodium undecylbenzene sulfonate, and specifically comprises the following steps: (1) Providing a chip wafer metal pad (commercially available, manufactured by Guangdong Fozhixin Microelectronics Technology Research Co., Ltd.) for electroplating copper pillars, the chip wafer metal pad includes, from bottom to top, a wafer substrate, a metal pad, an insulating layer, a metallization layer, a photoresist, and microholes on the photoresist to expose the metallization layer, so as to facilitate the subsequent electroplating of copper pillars; The thickness of the photoresist is 50 μm, the diameter of the micropores thereon is 80 μm, and the spacing between the micropores is 150 μm; The metallization layer includes an adhesion layer and a Cu seed layer sputtered on the surface of the adhesion layer; wherein the adhesion layer can enhance the adhesion between metals, so that the upper and lower layers are firmly adhered and not easy to peel off, and the Cu seed layer is composed of a 100nm Ti barrier layer and a 300nm copper seed layer sputtered by PVD technology, so that the subsequent copper electroplating process can be realized; (2) Use air plasma to clean the metal pad of the chip wafer for 20 seconds, then immerse it in a 50g / L sulfuric acid solution and remove bubbles by shaking. This can remove impurities and bubbles at the bottom of the micropores and increase the wettability of subsequent electroplating. (3) Place the copper column in a copper column electroplating solution for electroplating at a current density of 10ASD (1ASD = A / dm 2 ), the electroplating time is 40min, the electroplating temperature is 30℃, and the stirring rate during the electroplating process is 30rpm; The components of the electroplating solution are: 200g / L copper sulfate pentahydrate, 80g / L sulfuric acid, Cl - 40 mg / L, 3-mercapto-1-propanesulfonic acid (sodium) salt (MPS) 30 mg / L, polyethylene glycol 1000 (PEG-1000) 40 mg / L, polyvinyl pyrrolidone (PVP-24000, average molecular weight 24000, purchased from Aladdin) 50 mg / L, sodium undecylbenzene sulfonate (purchased from Xibao Biotechnology (Shanghai) Co., Ltd.) 20 mg / L, solvent water; (4) After electroplating, the substrate is washed with water and then the photoresist is removed with a mixed solution of TMAH and DMSO (mass ratio is 1:1) to expose the deposited copper pillars.

[0029] Example 6 The difference between this embodiment and embodiment 1 is that the alkylbenzene sulfonate in this embodiment is sodium octadecylbenzene sulfonate, and specifically comprises the following steps: (1) Providing a chip wafer metal pad (commercially available, manufactured by Guangdong Fozhixin Microelectronics Technology Research Co., Ltd.) for electroplating copper pillars, the chip wafer metal pad includes, from bottom to top, a wafer substrate, a metal pad, an insulating layer, a metallization layer, a photoresist, and microholes on the photoresist to expose the metallization layer, so as to facilitate the subsequent electroplating of copper pillars; The thickness of the photoresist is 50 μm, the diameter of the micropores thereon is 80 μm, and the spacing between the micropores is 150 μm; The metallization layer includes an adhesion layer and a Cu seed layer sputtered on the surface of the adhesion layer; wherein the adhesion layer can enhance the adhesion between metals, so that the upper and lower layers are firmly adhered and not easy to peel off, and the Cu seed layer is composed of a 100nm Ti barrier layer and a 300nm copper seed layer sputtered by PVD technology, so that the subsequent copper electroplating process can be realized; (2) Use air plasma to clean the metal pad of the chip wafer for 20 seconds, then immerse it in a 50g / L sulfuric acid solution and remove bubbles by shaking. This can remove impurities and bubbles at the bottom of the micropores and increase the wettability of subsequent electroplating. (3) Place the copper column in a copper column electroplating solution for electroplating at a current density of 10ASD (1ASD = A / dm2 ), the electroplating time is 40min, the electroplating temperature is 30℃, and the stirring rate during the electroplating process is 30rpm; The components of the electroplating solution are: 200g / L copper sulfate pentahydrate, 80g / L sulfuric acid, Cl - 40mg / L, 3-mercapto-1-propanesulfonic acid (sodium) salt (MPS) 30mg / L, polyethylene glycol 1000 (PEG-1000) 40mg / L, polyvinyl pyrrolidone (PVP-24000, average molecular weight 24000, purchased from Aladdin) 50mg / L, sodium octadecylbenzenesulfonate (purchased from Hubei Wonder Chemical Co., Ltd.) 20mg / L, solvent water; (4) After electroplating, the substrate is washed with water and then the photoresist is removed with a mixed solution of TMAH and DMSO (mass ratio is 1:1) to expose the deposited copper pillars.

[0030] Example 7 The difference between this embodiment and embodiment 1 is that the mass ratio of PVP to alkylbenzene sulfonate in this embodiment is 0.5, and specifically comprises the following steps: (1) Providing a chip wafer metal pad (commercially available, manufactured by Guangdong Fozhixin Microelectronics Technology Research Co., Ltd.) for electroplating copper pillars, the chip wafer metal pad includes, from bottom to top, a wafer substrate, a metal pad, an insulating layer, a metallization layer, a photoresist, and microholes on the photoresist to expose the metallization layer, so as to facilitate the subsequent electroplating of copper pillars; The thickness of the photoresist is 50 μm, the diameter of the micropores thereon is 80 μm, and the spacing between the micropores is 150 μm; The metallization layer includes an adhesion layer and a Cu seed layer sputtered on the surface of the adhesion layer; wherein the adhesion layer can enhance the adhesion between metals, so that the upper and lower layers are firmly adhered and not easy to peel off, and the Cu seed layer is composed of a 100nm Ti barrier layer and a 300nm copper seed layer sputtered by PVD technology, so that the subsequent copper electroplating process can be realized; (2) Use air plasma to clean the metal pad of the chip wafer for 20 seconds, then immerse it in a 50g / L sulfuric acid solution and remove bubbles by shaking. This can remove impurities and bubbles at the bottom of the micropores and increase the wettability of subsequent electroplating. (3) Place the copper column in a copper column electroplating solution for electroplating at a current density of 10ASD (1ASD = A / dm 2 ), the electroplating time is 40min, the electroplating temperature is 30℃, and the stirring rate during the electroplating process is 30rpm; The components of the electroplating solution are: 200g / L copper sulfate pentahydrate, 80g / L sulfuric acid, Cl -40mg / L, 3-mercapto-1-propanesulfonic acid (sodium) salt (MPS) 30mg / L, polyethylene glycol 1000 (PEG-1000) 40mg / L, polyvinyl pyrrolidone (PVP-24000, average molecular weight 24000, purchased from Aladdin) 23.3mg / L, sodium dodecylbenzene sulfonate (purchased from Shandong Yonglida New Materials Technology Co., Ltd.) 46.7mg / L, solvent water; (4) After electroplating, the substrate is washed with water and then the photoresist is removed with a mixed solution of TMAH and DMSO (mass ratio is 1:1) to expose the deposited copper pillars.

[0031] Example 8 The difference between this embodiment and embodiment 1 is that the mass ratio of PVP to alkylbenzene sulfonate in this embodiment is 1, and specifically comprises the following steps: (1) Providing a chip wafer metal pad (commercially available, manufactured by Guangdong Fozhixin Microelectronics Technology Research Co., Ltd.) for electroplating copper pillars, the chip wafer metal pad includes, from bottom to top, a wafer substrate, a metal pad, an insulating layer, a metallization layer, a photoresist, and microholes on the photoresist to expose the metallization layer, so as to facilitate the subsequent electroplating of copper pillars; The thickness of the photoresist is 50 μm, the diameter of the micropores thereon is 80 μm, and the spacing between the micropores is 150 μm; The metallization layer includes an adhesion layer and a Cu seed layer sputtered on the surface of the adhesion layer; wherein the adhesion layer can enhance the adhesion between metals, so that the upper and lower layers are firmly adhered and not easy to peel off, and the Cu seed layer is composed of a 100nm Ti barrier layer and a 300nm copper seed layer sputtered by PVD technology, so that the subsequent copper electroplating process can be realized; (2) Use air plasma to clean the metal pad of the chip wafer for 20 seconds, then immerse it in a 50g / L sulfuric acid solution and remove bubbles by shaking. This can remove impurities and bubbles at the bottom of the micropores and increase the wettability of subsequent electroplating. (3) Place the copper column in a copper column electroplating solution for electroplating at a current density of 10ASD (1ASD = A / dm 2 ), the electroplating time is 40min, the electroplating temperature is 30℃, and the stirring rate during the electroplating process is 30rpm; The components of the electroplating solution are: 200g / L copper sulfate pentahydrate, 80g / L sulfuric acid, Cl - 40mg / L, 3-mercapto-1-propanesulfonic acid (sodium) salt (MPS) 30mg / L, polyethylene glycol 1000 (PEG-1000) 40mg / L, polyvinyl pyrrolidone (PVP-24000, average molecular weight 24000, purchased from Aladdin) 35mg / L, sodium dodecylbenzene sulfonate (purchased from Shandong Yonglida New Materials Technology Co., Ltd.) 35mg / L, solvent water; (4) After electroplating, the substrate is washed with water and then the photoresist is removed with a mixed solution of TMAH and DMSO (mass ratio is 1:1) to expose the deposited copper pillars.

[0032] Example 9 The difference between this embodiment and embodiment 1 is that the mass ratio of PVP to alkylbenzene sulfonate in this embodiment is 3, and specifically comprises the following steps: (1) Providing a chip wafer metal pad (commercially available, manufactured by Guangdong Fozhixin Microelectronics Technology Research Co., Ltd.) for electroplating copper pillars, the chip wafer metal pad includes, from bottom to top, a wafer substrate, a metal pad, an insulating layer, a metallization layer, a photoresist, and microholes on the photoresist to expose the metallization layer, so as to facilitate the subsequent electroplating of copper pillars; The thickness of the photoresist is 50 μm, the diameter of the micropores thereon is 80 μm, and the spacing between the micropores is 150 μm; The metallization layer includes an adhesion layer and a Cu seed layer sputtered on the surface of the adhesion layer; wherein the adhesion layer can enhance the adhesion between metals, so that the upper and lower layers are firmly adhered and not easy to peel off, and the Cu seed layer is composed of a 100nm Ti barrier layer and a 300nm copper seed layer sputtered by PVD technology, so that the subsequent copper electroplating process can be realized; (2) Use air plasma to clean the metal pad of the chip wafer for 20 seconds, then immerse it in a 50g / L sulfuric acid solution and remove bubbles by shaking. This can remove impurities and bubbles at the bottom of the micropores and increase the wettability of subsequent electroplating. (3) Place the copper column in a copper column electroplating solution for electroplating at a current density of 10ASD (1ASD = A / dm 2 ), the electroplating time is 40min, the electroplating temperature is 30℃, and the stirring rate during the electroplating process is 30rpm; The components of the electroplating solution are: 200g / L copper sulfate pentahydrate, 80g / L sulfuric acid, Cl - 40mg / L, 3-mercapto-1-propanesulfonic acid (sodium) salt (MPS) 30mg / L, polyethylene glycol 1000 (PEG-1000) 40mg / L, polyvinyl pyrrolidone (PVP-24000, average molecular weight 24000, purchased from Aladdin) 52.5mg / L, sodium dodecylbenzene sulfonate (purchased from Shandong Yonglida New Materials Technology Co., Ltd.) 17.5mg / L, solvent water; (4) After electroplating, the substrate is washed with water and then the photoresist is removed with a mixed solution of TMAH and DMSO (mass ratio is 1:1) to expose the deposited copper pillars.

[0033] Example 10 The difference between this embodiment and embodiment 1 is that the mass ratio of PVP to alkylbenzene sulfonate in this embodiment is 6, and specifically comprises the following steps: (1) Providing a chip wafer metal pad (commercially available, manufactured by Guangdong Fozhixin Microelectronics Technology Research Co., Ltd.) for electroplating copper pillars, the chip wafer metal pad includes, from bottom to top, a wafer substrate, a metal pad, an insulating layer, a metallization layer, a photoresist, and microholes on the photoresist to expose the metallization layer, so as to facilitate the subsequent electroplating of copper pillars; The thickness of the photoresist is 50 μm, the diameter of the micropores thereon is 80 μm, and the spacing between the micropores is 150 μm; The metallization layer includes an adhesion layer and a Cu seed layer sputtered on the surface of the adhesion layer; wherein the adhesion layer can enhance the adhesion between metals, so that the upper and lower layers are firmly adhered and not easy to peel off, and the Cu seed layer is composed of a 100nm Ti barrier layer and a 300nm copper seed layer sputtered by PVD technology, so that the subsequent copper electroplating process can be realized; (2) Use air plasma to clean the metal pad of the chip wafer for 20 seconds, then immerse it in a 50g / L sulfuric acid solution and remove bubbles by shaking. This can remove impurities and bubbles at the bottom of the micropores and increase the wettability of subsequent electroplating. (3) Place the copper column in a copper column electroplating solution for electroplating at a current density of 10ASD (1ASD = A / dm 2 ), the electroplating time is 40min, the electroplating temperature is 30℃, and the stirring rate during the electroplating process is 30rpm; The components of the electroplating solution are: 200g / L copper sulfate pentahydrate, 80g / L sulfuric acid, Cl - 40mg / L, 3-mercapto-1-propanesulfonic acid (sodium) salt (MPS) 30mg / L, polyethylene glycol 1000 (PEG-1000) 40mg / L, polyvinyl pyrrolidone (PVP-24000, average molecular weight 24000, purchased from Aladdin) 60mg / L, sodium dodecylbenzene sulfonate (purchased from Shandong Yonglida New Materials Technology Co., Ltd.) 10mg / L, solvent water; (4) After electroplating, the substrate is washed with water and then the photoresist is removed with a mixed solution of TMAH and DMSO (mass ratio is 1:1) to expose the deposited copper pillars.

[0034] Embodiment 11 The difference between this embodiment and embodiment 1 is that the current density in this embodiment is 3A / dm 2 , specifically including the following steps: (1) Providing a chip wafer metal pad (commercially available, manufactured by Guangdong Fozhixin Microelectronics Technology Research Co., Ltd.) for electroplating copper pillars, the chip wafer metal pad includes, from bottom to top, a wafer substrate, a metal pad, an insulating layer, a metallization layer, a photoresist, and microholes on the photoresist to expose the metallization layer, so as to facilitate the subsequent electroplating of copper pillars; The thickness of the photoresist is 50 μm, the diameter of the micropores thereon is 80 μm, and the spacing between the micropores is 150 μm; The metallization layer includes an adhesion layer and a Cu seed layer sputtered on the surface of the adhesion layer; wherein the adhesion layer can enhance the adhesion between metals, so that the upper and lower layers are firmly adhered and not easy to peel off, and the Cu seed layer is composed of a 100nm Ti barrier layer and a 300nm copper seed layer sputtered by PVD technology, so that the subsequent copper electroplating process can be realized; (2) Use air plasma to clean the metal pad of the chip wafer for 20 seconds, then immerse it in a 50g / L sulfuric acid solution and remove bubbles by shaking. This can remove impurities and bubbles at the bottom of the micropores and increase the wettability of subsequent electroplating. (3) Place the copper column in the electroplating solution for electroplating, and the electroplating current density is 3ASD (1ASD = A / dm 2 ), the electroplating time is 40min, the electroplating temperature is 30℃, and the stirring rate during the electroplating process is 30rpm; The components of the electroplating solution are: 200g / L copper sulfate pentahydrate, 80g / L sulfuric acid, Cl - 40mg / L, 3-mercapto-1-propanesulfonic acid (sodium) salt (MPS) 30mg / L, polyethylene glycol 1000 (PEG-1000) 40mg / L, polyvinyl pyrrolidone (PVP-24000, average molecular weight 24000, purchased from Aladdin) 50mg / L, sodium dodecylbenzene sulfonate (purchased from Shandong Yonglida New Materials Technology Co., Ltd.) 20mg / L, solvent water; (4) After electroplating, the substrate is washed with water and then the photoresist is removed with a mixed solution of TMAH and DMSO (mass ratio is 1:1) to expose the deposited copper pillars.

[0035] Example 12 The difference between this embodiment and embodiment 1 is that the current density in this embodiment is 5A / dm 2 , specifically including the following steps: (1) Providing a chip wafer metal pad (commercially available, manufactured by Guangdong Fozhixin Microelectronics Technology Research Co., Ltd.) for electroplating copper pillars, the chip wafer metal pad includes, from bottom to top, a wafer substrate, a metal pad, an insulating layer, a metallization layer, a photoresist, and microholes on the photoresist to expose the metallization layer, so as to facilitate the subsequent electroplating of copper pillars; The thickness of the photoresist is 50 μm, the diameter of the micropores thereon is 80 μm, and the spacing between the micropores is 150 μm; The metallization layer includes an adhesion layer and a Cu seed layer sputtered on the surface of the adhesion layer; wherein the adhesion layer can enhance the adhesion between metals, so that the upper and lower layers are firmly adhered and not easy to peel off, and the Cu seed layer is composed of a 100nm Ti barrier layer and a 300nm copper seed layer sputtered by PVD technology, so that the subsequent copper electroplating process can be realized; (2) Use air plasma to clean the metal pad of the chip wafer for 20 seconds, then immerse it in a 50g / L sulfuric acid solution and remove bubbles by shaking. This can remove impurities and bubbles at the bottom of the micropores and increase the wettability of subsequent electroplating. (3) Place the copper column in the electroplating solution for electroplating, and the electroplating current density is 5ASD (1ASD = A / dm 2 ), the electroplating time is 40min, the electroplating temperature is 30℃, and the stirring rate during the electroplating process is 30rpm; The components of the electroplating solution are: 200g / L copper sulfate pentahydrate, 80g / L sulfuric acid, Cl - 40mg / L, 3-mercapto-1-propanesulfonic acid (sodium) salt (MPS) 30mg / L, polyethylene glycol 1000 (PEG-1000) 40mg / L, polyvinyl pyrrolidone (PVP-24000, average molecular weight 24000, purchased from Aladdin) 50mg / L, sodium dodecylbenzene sulfonate (purchased from Shandong Yonglida New Materials Technology Co., Ltd.) 20mg / L, solvent water; (4) After electroplating, the substrate is washed with water and then the photoresist is removed with a mixed solution of TMAH and DMSO (mass ratio is 1:1) to expose the deposited copper pillars.

[0036] Example 13 The difference between this embodiment and embodiment 1 is that the current density in this embodiment is 20A / dm 2 , specifically including the following steps: (1) Providing a chip wafer metal pad (commercially available, manufactured by Guangdong Fozhixin Microelectronics Technology Research Co., Ltd.) for electroplating copper pillars, wherein the chip wafer metal pad includes, from bottom to top, a wafer substrate, a metal pad, an insulating layer, a metallization layer, a photoresist, and microholes on the photoresist, wherein the microholes expose the metallization layer to facilitate subsequent electroplating; The thickness of the photoresist is 50 μm, the diameter of the micropores thereon is 80 μm, and the spacing between the micropores is 150 μm; The metallization layer includes an adhesion layer and a Cu seed layer sputtered on the surface of the adhesion layer; wherein the adhesion layer can enhance the adhesion between metals, so that the upper and lower layers are firmly adhered and not easy to peel off, and the Cu seed layer is composed of a 100nm Ti barrier layer and a 300nm copper seed layer sputtered by PVD technology, so that the subsequent copper electroplating process can be realized; (2) Use air plasma to clean the metal pad of the chip wafer for 20 seconds, then immerse it in a 50g / L sulfuric acid solution and remove bubbles by shaking. This can remove impurities and bubbles at the bottom of the micropores and increase the wettability of subsequent electroplating. (3) Place the copper column in the electroplating solution for electroplating, and the electroplating current density is 20ASD (1ASD=A / dm 2 ), the electroplating time is 40min, the electroplating temperature is 30℃, and the stirring rate during the electroplating process is 30rpm; The components of the electroplating solution are: 200g / L copper sulfate pentahydrate, 80g / L sulfuric acid, Cl - 40mg / L, 3-mercapto-1-propanesulfonic acid (sodium) salt (MPS) 30mg / L, polyethylene glycol 1000 (PEG-1000) 40mg / L, polyvinyl pyrrolidone (PVP-24000, average molecular weight 24000, purchased from Aladdin) 50mg / L, sodium dodecylbenzene sulfonate (purchased from Shandong Yonglida New Materials Technology Co., Ltd.) 20mg / L, solvent water; (4) After electroplating, the substrate is washed with water and then the photoresist is removed with a mixed solution of TMAH and DMSO (mass ratio is 1:1) to expose the deposited copper pillars.

[0037] Embodiment 14 The difference between this embodiment and embodiment 1 is that the current density in this embodiment is 40A / dm 2 , specifically including the following steps: (1) Providing a chip wafer metal pad (commercially available, manufactured by Guangdong Fozhixin Microelectronics Technology Research Co., Ltd.) for electroplating copper pillars, wherein the chip wafer metal pad includes, from bottom to top, a wafer substrate, a metal pad, an insulating layer, a metallization layer, a photoresist, and microholes on the photoresist, wherein the microholes expose the metallization layer to facilitate subsequent electroplating; The thickness of the photoresist is 50 μm, the diameter of the micropores thereon is 80 μm, and the spacing between the micropores is 150 μm; The metallization layer includes an adhesion layer and a Cu seed layer sputtered on the surface of the adhesion layer; wherein the adhesion layer can enhance the adhesion between metals, so that the upper and lower layers are firmly adhered and not easy to peel off, and the Cu seed layer is composed of a 100nm Ti barrier layer and a 300nm copper seed layer sputtered by PVD technology, so that the subsequent copper electroplating process can be realized; (2) Use air plasma to clean the metal pad of the chip wafer for 20 seconds, then immerse it in a 50g / L sulfuric acid solution and remove bubbles by shaking. This can remove impurities and bubbles at the bottom of the micropores and increase the wettability of subsequent electroplating. (3) Place the copper column in the electroplating solution for electroplating, and the electroplating current density is 40ASD (1ASD=A / dm 2 ), the electroplating time is 40min, the electroplating temperature is 30℃, and the stirring rate during the electroplating process is 30rpm; The components of the electroplating solution are: 200g / L copper sulfate pentahydrate, 80g / L sulfuric acid, Cl - 40mg / L, 3-mercapto-1-propanesulfonic acid (sodium) salt (MPS) 30mg / L, polyethylene glycol 1000 (PEG-1000) 40mg / L, polyvinyl pyrrolidone (PVP-24000, average molecular weight 24000, purchased from Aladdin) 50mg / L, sodium dodecylbenzene sulfonate (purchased from Shandong Yonglida New Materials Technology Co., Ltd.) 20mg / L, solvent water; (4) After electroplating, the substrate is washed with water and then the photoresist is removed with a mixed solution of TMAH and DMSO (mass ratio is 1:1) to expose the deposited copper pillars.

[0038] Comparative Example 1 The difference between this comparative example and Example 1 is that there is no PVP-24000 in the electroplating solution of this comparative example.

[0039] Comparative Example 2 The difference between this comparative example and Example 1 is that the electroplating solution of this comparative example does not contain sodium dodecylbenzene sulfonate.

[0040] Comparative Example 3 The difference between this comparative example and Example 1 is that the electroplating solution of this comparative example does not contain PVP-24000 and sodium dodecylbenzene sulfonate.

[0041] Comparative Example 4 The difference between this comparative example and Example 1 is that in this comparative example, the sodium dodecylbenzene sulfonate in the electroplating solution is replaced with sodium dodecylbenzene sulfonate of equal mass concentration.

[0042] Comparative Example 5 The difference between this comparative example and Example 1 is that the concentration of PVP-24000 in the electroplating solution of this comparative example is 5 mg / L.

[0043] Comparative Example 6 The difference between this comparative example and Example 1 is that the concentration of PVP-24000 in the electroplating solution of this comparative example is 80 mg / L.

[0044] Comparative Example 7 The difference between this comparative example and Example 1 is that the concentration of sodium dodecylbenzene sulfonate in the electroplating solution of this comparative example is 5 mg / L.

[0045] Comparative Example 8 The difference between this comparative example and Example 1 is that the concentration of sodium dodecylbenzene sulfonate in the electroplating solution of this comparative example is 60 mg / L.

[0046] AOI (Automated Optical Inspection) is used with the aid of a scanning electron microscope to inspect the copper pillars. The inspection index is the detection of defects such as holes and gaps in the cross-section of the copper pillars. The proportion of defect-free copper pillars among 100 copper pillars is calculated to examine the defect-free condition of the electroplated copper pillars, that is, the qualified rate (expressed as a percentage: %).

[0047] The copper pillars prepared as above were subjected to mechanical property tests. The testing equipment was a bonding strength tester (PTR-1102). During the shear experiment, the electroplated chip was fixed on the testing machine. Due to the large blade head, a row of 4 copper pillars on the chip were subjected to shear tests during the test. The shear blade head was 2 μm away from the sample seed layer, and the shear speed was 6 mm / min. After multiple measurements and taking the average value, 1 / 4 of the average value was the mechanical property of a single copper pillar.

[0048] Table 1 It can be seen from the above embodiments that the method for preparing copper pillars by electroplating of the present invention can produce copper pillars with good mechanical properties and fewer defects, and can improve the reliability of subsequent copper pillar interconnections, wherein the shear force of the copper pillars is ≥150MPa, and the probability of no defective copper pillars on the wafer is greater than 85%.

[0049] It can be seen from Example 1 and Comparative Examples 1-8 that the polyvinyl pyrrolidone and alkylbenzene sulfonate in the electroplating solution of the present invention have the effect of synergistically improving the shear force of the copper column obtained and reducing the number of defects of the copper column, and the dosage of polyvinyl pyrrolidone and alkylbenzene sulfonate will also have a significant effect on the electroplating quality of the copper column. Therefore, when the concentration of polyvinyl pyrrolidone is selected to be 10-70 mg / L and the concentration of alkylbenzene sulfonate is 10-50 mg / L in the electroplating process of the present invention, the copper column obtained meets the requirements.

[0050] It can be seen from Examples 1-4 that the molecular weight of polyvinyl pyrrolidone has a certain influence on the shear force and the number of defects of the copper column. Preferably, the number average molecular weight of the polyvinyl pyrrolidone is 3500-40000, and more preferably 10000-24000.

[0051] It can be seen from Examples 1 and 5-6 that the number of carbon atoms on the alkyl group of alkylbenzene sulfonate has a certain influence on the shear force and the number of defects of the copper column. The number of carbon atoms on the alkyl group of alkylbenzene sulfonate is preferably 11-19, and more preferably 12-18.

[0052] It can be seen from Examples 1 and 7-10 that the mass ratio of polyvinyl pyrrolidone to alkylbenzene sulfonate has an effect on the shear force and defects of the copper column. When the mass ratio of polyvinyl pyrrolidone to alkylbenzene sulfonate is (0.5-6):1, and more preferably, the mass ratio of polyvinyl pyrrolidone to alkylbenzene sulfonate is (1-3):1, the copper column of the present invention has good shear force and a small number of defects.

[0053] It can be seen from Examples 1 and 11-14 that the current density of the electroplating process has an effect on the deposition rate of copper. In combination with the specific electroplating solution of the present invention, the electroplating system of the present invention is adapted to a wider current density. The appropriate current density and the specific electroplating solution cooperate with each other and can be used in a current density of 3-40 A / dm 2 The electroplating is carried out under the above conditions, and the mechanical properties of the copper pillars are relatively good, and the defects of the copper pillars are relatively few.

[0054] Finally, it should be noted that the above embodiments are only used to illustrate the technical solution of the present invention rather than to limit the scope of protection of the present invention. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solution of the present invention can be modified or replaced by equivalents without departing from the essence and scope of the technical solution of the present invention.

Claims

1. A method for electroplating wafer-level copper pillars, characterized in that: The steps include: (1) Providing chip wafer metal pads to be electroplated; (2) subjecting the metal pads of the chip wafer to be electroplated to air plasma cleaning and acid immersion in sequence; (3) electroplating the metal pads of the chip wafer to be electroplated after acid immersion in step (2) in an electroplating solution, and then cleaning and debonding to obtain the copper pillars; The electroplating solution includes the following components: 100-300 g / L copper sulfate, 40-100 g / L sulfuric acid, Cl - 30-60mg / L, accelerator 25-60mg / L, polyethylene glycol 10-80mg / L, polyvinyl pyrrolidone 10-70mg / L, alkyl benzene sulfonate 10-50mg / L, and the balance water.

2. The electroplating method of wafer-level copper pillars according to claim 1, characterized in that: The number average molecular weight of the polyvinyl pyrrolidone is 3500-40000.

3. The electroplating method of wafer-level copper pillars according to claim 1, characterized in that: The alkylbenzene sulfonate includes at least one of undecylbenzene sulfonate, dodecylbenzene sulfonate, tridecylbenzene sulfonate, tetradecylbenzene sulfonate, pentadecylbenzene sulfonate, hexadecylbenzene sulfonate, heptadecylbenzene sulfonate, octadecylbenzene sulfonate and nonadecylbenzene sulfonate.

4. The electroplating method of wafer-level copper pillars according to claim 1, characterized in that: The mass ratio of the polyvinyl pyrrolidone to the alkylbenzene sulfonate is (0.5-6):

1.

5. The electroplating method of wafer-level copper pillars as claimed in claim 4, characterized in that: The mass ratio of the polyvinyl pyrrolidone to the alkylbenzene sulfonate is (1-3):

1.

6. The electroplating method of wafer-level copper pillars according to claim 1, characterized in that: The polyethylene glycol includes at least one of PEG-200, PEG-400, PEG-600, PEG-800, PEG-1000, PEG-2000, PEG-3000, PEG-4000, PEG-6000, PEG-8000, PEG-10000, and PEG-20000.

7. The electroplating method of wafer-level copper pillars as claimed in claim 1, characterized in that: The accelerator includes at least one of 3-mercapto-1-propane sulfonate, polydisulfide propane sulfonate, 3-mercapto-ethyl sulfonate, and 3-mercapto-1-ethane sulfonic acid potassium salt.

8. The electroplating method of wafer-level copper pillars as claimed in claim 1, characterized in that: The current density of the electroplating is 3-40A / dm 2 , the electroplating time is 10-60min.

9. The electroplating method of wafer-level copper pillars according to claim 1, characterized in that: The acid used in the acid leaching is a 20-80 g / L sulfuric acid aqueous solution, and the solvents used in the degumming are tetramethylammonium hydroxide and dimethyl sulfoxide.

10. A wafer, characterized in that: The invention comprises a wafer substrate, a metal pad, an insulating layer and a metallization layer in sequence, and a copper column made on the metallization layer by the electroplating method of the wafer-level copper column according to any one of claims 1 to 9.

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