Copper electroplating leveling agent and preparation method, electroplating solution, electroplating method and product

Abstract

The invention discloses a copper electroplating leveler and a preparation method, an electroplating solution, an electroplating method and a product, and belongs to the field of copper electroplating technology. The leveler is obtained by reacting 1,3,5-tris(4-pyridyl)benzene with a compound containing halogen and hydroxyl at the same time, and the electroplating solution components include: copper sulfate, sulfuric acid, chloride ions, an accelerator, an inhibitor and a leveler, and the current density during electroplating is 1-15ASD, and the electroplating temperature is 18-45°C. The copper electroplating leveler and the corresponding electroplating solution provided by the present invention can be used for electroplating copper columns and for electroplating copper RDLs. There is no need to change the plating solution when producing switching copper columns and copper RDL products, and the electroplating solution has excellent performance. The obtained copper column has good uniformity: WID% <5%; the copper column has a flat morphology TIR% <5%; the copper RDL line profile is flat, has no appearance defects, and has good uniformity: WID% <5%.

Description

Technical Field

[0001] The invention belongs to the technical field of copper electroplating, and relates to a copper electroplating leveler and a preparation method thereof, an electroplating solution, an electroplating method and a product. Background Art

[0002] Electroplated copper pillars (Copper pillar) and copper redistribution layer (RDL) are one of the key technologies in semiconductor packaging, mainly used to provide electrical interconnection and mechanical support. When forming an array of solder pillars on the surface of an integrated circuit chip, it is crucial to achieve finer pitches to increase integration density. At present, attempts are being made to replace these solder pillars with copper pillars or columns formed on the metal under the pillars by electroplating. Copper RDL technology is mainly used in fan-in and fan-out packaging scenarios. By electroplating copper, electrical connections between different functional areas inside the chip and the outside are achieved, which can meet the needs of higher integration and more compact packaging.

[0003] CN109996785B discloses an electrodeposition composition for copper deposition in wafer-level packaging of integrated circuits, the composition comprising: (a) a copper ion source; (b) an acid; (c) an inhibitor; and (d) a leveler, wherein the leveler comprises a quaternized bipyridyl compound prepared by reacting a bipyridyl compound with a difunctional alkylating agent, or a quaternized poly(epichlorohydrin).

[0004] CN102362013B discloses a method for metallizing a through-hole feature in a semiconductor integrated circuit device substrate, comprising contacting the semiconductor integrated circuit device substrate with an electrolytic copper deposition chemistry, the electrolytic copper deposition chemistry comprising (a) a copper ion source and (b) a leveler compound, wherein the leveler compound is a reaction product of a bipyridyl compound and an alkylating agent; and supplying an electric current to the electrolytic deposition chemistry to deposit copper metal on the bottom and sidewalls of the through-hole feature, thereby obtaining a copper-filled through-hole.

[0005] CN107541757B discloses a method for electroplating a photoresist-defined feature from a copper electroplating bath comprising a reaction product of a pyrazole compound and a diepoxide for electroplating a copper pillar. The copper electroplating bath comprises one or more reaction products of one or more pyrazole compounds and one or more diepoxides; an electrolyte; one or more accelerators; and one or more inhibitors.

[0006] CN110577497B discloses an indanthrone quaternary ammonium salt compound and a preparation method and application thereof. The indanthrone quaternary ammonium salt compound can have a larger coverage area on the electrode surface and can increase cathode polarization, inhibit copper deposition, thereby making the electroplated particles finer and allowing the copper-plated layer to obtain a high preferred crystal plane orientation, so that it can be used as a quaternary ammonium salt leveler for acidic copper electroplating.

[0007] CN111074306B discloses a copper column electroplating solution and an electroplating method suitable for ultra-large current density. The copper column electroplating solution includes: copper methanesulfonate: 150-240g / L, methanesulfonic acid: 40-70g / L, chloride ion: 30-50mg / L, sodium polydisulfide dipropane sulfonate: 2-5mg / L, polyethylene glycol: 40-100mg / L, Yanlu green: 40-80mg / L; DI pure water: balance.

[0008] However, there are still many challenges in controlling the electroplating process to obtain copper pillars and copper RDLs of the required shape for semiconductor packaging. Although the main shape of the copper pillar can be determined by confining it to a hole formed by the sidewalls of the dielectric material, the shape of the end of the pillar is often unsatisfactory, with problems such as excessive protrusions, depressions or irregularities. At the same time, the electroplated copper pillars also need to meet the requirements of smooth and defect-free surfaces to improve welding quality. Electroplated copper pillars must also prevent the formation of Kirkendall voids to avoid affecting electrical properties, mechanical strength and process stability. At present, the main defects in the process of electroplating copper RDL are insufficient electroplating uniformity and defects in circuit appearance. Uneven thickness of the electroplated copper layer will lead to inconsistent electrical properties, which in turn affects the electrical performance stability of the chip.

[0009] At present, the copper pillars and RDLs required for semiconductor packaging have the following main technical problems in the electroplating process. (1) Poor uniformity of copper pillar electroplating height: One of the main functions of copper pillars is to provide connections between chips or between chips and silicon adapters, so their height must be as uniform as possible. If the electroplating height is uneven, the copper layer thickness in some areas may be thinner and the copper layer in other areas may be thicker. This may lead to differences in the area of ​​​​the solder balls during the flip-chip packaging process, resulting in resistance differences at each bump position or even short circuits, which will affect the speed and stability of electrical signal transmission and may seriously cause the device to work abnormally or fail. (2) Poor surface quality and electroplating height uniformity of copper RDL: In high-speed signal transmission, electrical signals are mainly transmitted on the surface of the conductor, which is the so-called skin effect. Surface defects or roughness may cause different signal transmission paths, that is, different resistances, affecting the quality and speed of signal transmission. Differences in the height of RDL copper circuits will lead to uneven resistance distribution, which in turn affects the quality of electrical signal transmission and may cause device failure. (3) Kirkendall voids exist after the copper pillars are reflowed. Kirkendall voids are caused by the formation of intermetallic compounds between copper and metals such as tin or nickel on top of it during the welding process, which forms voids due to the different densities between different metals. The formation of voids may cause the conductivity of the copper layer to decrease in local areas, thereby affecting the overall resistance and electrical properties of the column, resulting in uneven resistance values, affecting the stability and speed of signal transmission. In addition, after the formation of voids, the mechanical strength and wear resistance of the copper column may be significantly reduced. When faced with temperature changes, vibrations or mechanical stress, these voids may become stress concentration points, causing damage or shedding of the copper layer or the entire column.

[0010] In addition, there are usually two types of electroplating solutions for copper pillars and RDLs on the market, using different additive systems. When using the same electroplating machine to produce different products, the plating solution needs to be replaced, which makes maintenance more troublesome. Summary of the invention

[0011] In order to solve the above-mentioned technical problems existing in the electroplating process of copper pillars and RDL required for semiconductor packaging, the inventors have designed and synthesized a new compound as an electroplating copper leveler after intensive research, and developed corresponding electroplating solution and electroplating method, which can be simultaneously applied to the electroplating of copper pillars and RDL in advanced packaging. The electroplated copper has no appearance defects and has good uniformity. The copper pillar contour is flat (TIR% < 5%), and the copper pillars and RDL have good uniformity within the chip (WID% < 5%).

[0012] The primary aspect of the present invention is to provide a copper electroplating leveler, the structure of which is shown in the following formula:

[0013] .

[0014] In the formula, A is an alkylene group having 1 to 4 carbon atoms, such as methylene, ethylene, propylene, or butylene; or it is a repeating unit having the structure -OCH2-CH2-, with the number of repeating units being 1 to 4; and X is Cl, Br, or I.

[0015] Preferably, the structure of the copper electroplating leveler is one of the following formulae:

[0016] ,

[0017] ,

[0018] ,

[0019] .

[0020] Another aspect of the present invention is to provide a method for preparing the aforementioned electroplating copper leveler, comprising the following steps:

[0021] S1. dissolving 1,3,5-tri(4-pyridyl)benzene in an organic solvent to obtain a 1,3,5-tri(4-pyridyl)benzene solution;

[0022] S2: adding a compound containing both halogen and hydroxyl to a 1,3,5-tri(4-pyridyl)benzene solution and heating for reaction;

[0023] After the reaction is completed, the solution is cooled and purified by column chromatography to obtain the compound product.

[0024] Furthermore, the organic solvent in step S1 is one or more of ethylene glycol, propylene glycol, glycerol, and ethylene glycol monomethyl ether.

[0025] Furthermore, the compound containing both halogen and hydroxyl in step S2 is 3-chloro-1-propanol, 2-chloroethoxyethanol or triethylene glycol monochlorohydrin.

[0026] Furthermore, in step S2, the reaction temperature is 160-180° C., and the reaction time is 0.5-2 h.

[0027] Furthermore, in step S2, the molar ratio of the compound containing both halogen and hydroxyl to 1,3,5-tri(4-pyridyl)benzene is (2.9-3.1):1.

[0028] Another aspect of the present invention is to provide an electroplating solution, the components of which include: copper sulfate, sulfuric acid, chloride ions, an accelerator, an inhibitor and the leveler provided by the present invention, the accelerator is one or two of sodium polydisulfide propane sulfonate (SPS) and sodium 3-mercapto-1-propane sulfonate (MPS), and the inhibitor is one or more of polyethylene glycol (PEG), polypropylene glycol (PPG), and ethylene glycol propylene glycol block copolymers (PEO-PPO-PEO and PPO-PEO-PPO).

[0029] Furthermore, the concentrations of the components are 20-50 g / L copper ion, 100-200 g / L sulfuric acid, 30-60 ppm chloride ion, 1-100 ppm accelerator, 10-200 ppm inhibitor, and 1-30 ppm leveler.

[0030] Another aspect of the present invention is to provide an electroplating method for the above electroplating solution, wherein the current density during electroplating is 1-15ASD (A / dm 2 ), within this current density range, the copper pillar and copper RDL can maintain a flat profile and good uniformity; the plating solution operating temperature range is 18-45℃, within this temperature range, the plating solution system can maintain good performance.

[0031] Another aspect of the present invention is to provide an electroplated product obtained from the above electroplating solution.

[0032] Furthermore, the electroplating products include copper pillars and copper redistribution layers for semiconductor packaging.

[0033] The present invention has the following beneficial technical effects: the electroplating copper leveler and the corresponding electroplating solution provided by the present invention can be used for electroplating copper pillars and copper RDLs, and there is no need to replace the plating solution when producing and switching copper pillars and copper RDL products, and the electroplating solution has excellent performance. The obtained copper pillars have good uniformity: WID% <5%; the copper pillars have flat morphology and TIR% <5%; the copper RDL line contour is flat, has no appearance defects, and has good uniformity: WID% <5%. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Figure 1 is a profile image of the copper pillar of Test Example 1.

[0035] Figure 2 is the RDL morphology profile of test example 1.

[0036] Figure 3 This is a profile image of the copper pillar of Test Example 2.

[0037] Figure 4 is the RDL morphology profile of test example 2.

[0038] Figure 5This is a profile image of the copper pillar of Test Example 3.

[0039] Figure 6 is the RDL morphology profile diagram of test example 3.

[0040] Figure 7 is a profile diagram of the copper pillar of Test Example 4.

[0041] Figure 8 is the RDL morphology profile diagram of test example 4.

[0042] Fig. 9 is a profile image of the copper pillar of Test Example 5.

[0043] Fig.10 is the RDL morphology profile diagram of test example 5.

[0044] Fig.11 is a profile image of the copper pillar of Test Example 6.

[0045] Fig.12 is the RDL morphology profile diagram of test example 6.

[0046] Fig.13 is a profile image of the copper pillar of Test Example 7.

[0047] Fig.14 is the RDL morphology profile diagram of test example 7.

[0048] Fig.15 is a profile diagram of the copper pillar of Test Example 8.

[0049] Fig.16 is the RDL morphology profile diagram of test example 8.

[0050] Fig.17 It is a profile diagram of the copper column morphology of test comparative example 1.

[0051] Fig.18 It is the RDL morphology profile diagram of test comparative example 1.

[0052] Fig.19 This is a SEM image of the copper pillar + tin-silver electroplating of Test Example 1 after 10 reflows. DETAILED DESCRIPTION

[0053] The technical solution of the present invention is described clearly and completely below in conjunction with the accompanying drawings of the specification. Obviously, the described implementation is only a part of the implementation of the present invention, not all of the implementations. Based on the implementation of the present invention, all other implementations obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention. Example 1

[0054] An electroplating copper leveler, the chemical structural formula is:

[0055] .

[0056] The synthesis method is as follows:

[0057] Add 20 mL of ethylene glycol to a two-necked flask equipped with a magnetic bar and a condenser, heat to 80°C, then add 3.2 mmol of 1,3,5-tri(4-pyridyl)benzene, and after it is completely dissolved, add 9.6 mmol of 3-chloro-1-propanol, heat to 170°C, and react at this temperature for 1 h. Allow the solution to cool to room temperature, purify by column chromatography, and use it directly after diluting with deionized water.

[0058] Nuclear magnetic resonance spectrum NMR (500MHz, DMSO- d 6 , 22℃):

[0059] 9.08(6H,ArH), 8.96(6H,ArH), 8.04(3H,ArH), 5.01(6H,CH2), 4.33(3H,OH), 3.49(6H,CH2), 2.22(6H,CH2). Example 2

[0060] An electroplating copper leveler, the chemical structural formula is:

[0061]

[0062] The synthesis method is as follows:

[0063] Add 20 mL of ethylene glycol to a two-necked flask equipped with a magnetic bar and a condenser, heat to 80°C, then add 3.2 mmol of 1,3,5-tri(4-pyridyl)benzene, and after it is completely dissolved, add 9.6 mmol of 2-chloroethoxyethanol, heat to 170°C, and react at this temperature for 1 h. Allow the solution to cool to room temperature, purify by column chromatography, and use it directly after diluting with deionized water.

[0064] Nuclear magnetic resonance spectrum NMR (500MHz, DMSO- d 6 , 22℃):

[0065] 9.09(6H,ArH), 8.98(6H,ArH), 8.07(3H,ArH), 5.02(3H,OH), 4.36(6H,CH2), 4.11(6H,CH2), 3.70(6H,CH2), 3.54(6H,CH2). Example 3

[0066] An electroplating copper leveler, the chemical structural formula is:

[0067]

[0068] The synthesis method is as follows:

[0069] Add 20 mL of ethylene glycol to a two-necked flask equipped with a magnetic rod and a condenser, heat to 80°C, then add 3.2 mmol of 1,3,5-tri-pyridylbenzene, and after it is completely dissolved, add 9.6 mmol of triethylene glycol monochlorohydrin, heat to 170°C, and react at this temperature for 1 h. Allow the solution to cool to room temperature, purify by column chromatography, and use it directly after diluting with deionized water.

[0070] Nuclear magnetic resonance spectrum NMR (500MHz, DMSO- d 6 , 22℃):

[0071] 9.11(6H,ArH), 8.99(6H,ArH), 8.06(3H,ArH), 4.33(6H,CH2), 4.21(6H,CH2),3.75(3H, OH), 3.67(6H,CH2), 3.58(6H,CH2), 3.52(6H,CH2), 3.50(6H,CH2).

[0072] Example 4

[0073] An electroplating copper leveler, the chemical structural formula is:

[0074]

[0075] The synthesis method is as follows:

[0076] Add 20 mL of ethylene glycol to a two-necked flask equipped with a magnetic bar and a condenser, heat to 80°C, then add 3.2 mmol of 1,3,5-tri-p-pyridylbenzene, and after it is completely dissolved, add 9.6 mmol of triethylene glycol monochlorohydrin, heat to 160°C, and react at this temperature for 1 h. Allow the solution to cool to room temperature, purify by column chromatography, and use it directly after diluting with deionized water. Example 5

[0077] An electroplating copper leveler, the chemical structural formula is:

[0078]

[0079] The synthesis method is as follows:

[0080] Add 20 mL of ethylene glycol to a two-necked flask equipped with a magnetic bar and a condenser, heat to 80°C, then add 3.2 mmol of 1,3,5-tri-pyridylbenzene, and after it is completely dissolved, add 9.6 mmol of triethylene glycol monochlorohydrin, heat to 180°C, and react at this temperature for 1 h. Allow the solution to cool to room temperature, purify by column chromatography, and use it directly after diluting with deionized water. Example 6

[0081] An electroplating copper leveler, the chemical structural formula is:

[0082]

[0083] The synthesis method is as follows:

[0084] Add 20 mL of ethylene glycol to a two-necked flask equipped with a magnetic rod and a condenser, heat to 80°C, then add 3.2 mmol of 1,3,5-tri-pyridylbenzene, and after it is completely dissolved, add 9.6 mmol of triethylene glycol monochlorohydrin, heat to 170°C, and react at this temperature for 0.5 h. Allow the solution to cool to room temperature, purify by column chromatography, and use it directly after diluting with deionized water. Example 7

[0085] An electroplating copper leveler, the chemical structural formula is:

[0086]

[0087] The synthesis method is as follows:

[0088] Add 20 mL of ethylene glycol to a two-necked flask equipped with a magnetic rod and a condenser, heat to 80°C, then add 3.2 mmol of 1,3,5-tri-pyridylbenzene, and after it is completely dissolved, add 9.6 mmol of triethylene glycol monochlorohydrin, heat to 170°C, and react at this temperature for 2 h. Allow the solution to cool to room temperature, purify by column chromatography, and use it directly after diluting with deionized water. Example 8

[0089] The compounds synthesized in Examples 1-3 were used as levelers for the electroplating solution, and were used in combination with accelerators and inhibitors as test examples for copper electroplating. At the same time, the electroplating solution without a leveler was used as a test control. The copper electroplating process uses a silicon wafer as a cathode, a copper plate as a soluble anode, and a rack plating process. The copper ions in the electroplating solution are provided by copper sulfate, and the chloride ions are provided by hydrochloric acid, with 40 g / L copper ions, 140 g / L sulfuric acid, and 50 ppm chloride ions; the accelerator is SPS, and the inhibitor is PEG4000, with concentrations as shown in Table 1. When electroplating copper columns, a current density of 3ASD is used for electroplating for 7.6 min, and then a current density of 8ASD is used for electroplating for 18.2 min; when electroplating copper RDL, a current density of 3ASD is used for electroplating for 4.5 min; the electroplating temperature is 25°C.

[0090] The parameter WID% is used to characterize the uniformity of the copper pillar and RDL, and the parameter TIR% is used to characterize the flatness of the copper pillar. The calculation formula is as follows, and the calculation results are shown in Table 1.

[0091]

[0092] In the formula, Height max , Height min and Height average They are the maximum, minimum and average height of the copper pillar or RDL respectively.

[0093]

[0094] In the formula, Height center , Height edge and Height max They are the center height, edge height and maximum height of the copper column respectively.

[0095] Table 1 Test conditions and results of test examples 1-8 and comparative example 1

[0096]

[0097] The copper pillar morphology and RDL morphology of test examples 1-8 are as follows: Figure 1-Figure 16 As shown in the figure, the image is a contour image generated by a laser confocal microscope. The copper column morphology and RDL morphology of the comparative example 1 are as follows: Fig.17 , Fig.18 As shown in the figure. The copper column diameter is 50μm and the electroplating height is 37μm; the RDL line width is 25μm and the electroplating height is 3μm. Figure 1-Figure 16It can be seen that after adding the synthesized leveling agent of the present invention to the electroplating solution system, the electroplated copper pillars and RDL have no appearance defects, the height uniformity of the copper pillars in the chip is between 2.2% and 2.9%, the copper pillars show slight depressions, and the TIR% is between -2.1% and -5.3%; the RDL line profile is flat, and the uniformity WID% in the chip is between 3.1-4.7%. Fig.17 , Fig.18 It can be seen that in the test comparative example 1, because the synthesized leveling agent molecules of the present invention were not added, the copper pillars after electroplating were seriously tilted and had deep depressions, and the RDL showed local burning and copper nodules on the surface. The copper pillars after electroplating in the test example 1 were subjected to tin-silver electroplating reflow 10 times, and the cross-sectional SEM image (magnification 5000 times) was as follows: Fig.19 As shown, the picture shows that after 10 reflows, only a small amount of Kirkendall voids remain.

[0098] The results of the above test examples and comparative test examples show that the copper electroplating leveler and the corresponding electroplating solution provided by the present invention can be used for electroplating copper pillars as well as for electroplating copper RDLs; they can significantly improve the electroplating effects of copper pillars and RDLs, and meet the requirements of semiconductor packaging: the obtained copper pillars have good uniformity (WID% <5%), the copper pillars have flat morphology (TIR% <5%), the copper RDL line contour is flat, has no appearance defects, and has good uniformity (WID% <5%).

[0099] Although the embodiments of the present invention have been shown and described above, it is understood that the above embodiments are exemplary and cannot be understood as limiting the present invention. A person skilled in the art may change, modify, replace and modify the above embodiments within the scope of the present invention without departing from the principles and purpose of the present invention. The protection scope of the present invention is defined by the claims and their equivalent technical solutions.

Claims

1. An electroplating solution, characterized in that: Its components include: copper sulfate, sulfuric acid, chloride ions, accelerator, inhibitor and leveler. The structure of the leveler is shown in the following formula: ， In the formula, A is an alkylene group having 1 to 4 carbon atoms, or a repeating unit having the structure -OCH2-CH2-, and the number of repeating units is 1 to 4; X is Cl, Br or I; The accelerator is one or both of sodium polydisulfide propane sulfonate and sodium 3-mercapto-1-propane sulfonate, and the inhibitor is one or more of polyethylene glycol, polypropylene glycol, and ethylene glycol propylene glycol block copolymer.

2. The electroplating solution according to claim 1, characterized in that The structure of the leveling agent is one of the following formulas: ， ， ， 。 3. The electroplating solution according to claim 1, characterized in that The concentrations of the components are respectively 20-50 g / L copper ion, 100-200 g / L sulfuric acid, 30-60 ppm chloride ion, 1-100 ppm accelerator, 10-200 ppm inhibitor, and 1-30 ppm leveler.

4. The electroplating solution according to claim 1, characterized in that The preparation method of the leveling agent comprises the following steps: S1. dissolving 1,3,5-tri(4-pyridyl)benzene in an organic solvent to obtain a 1,3,5-tri(4-pyridyl)benzene solution; S2: Add a compound containing both halogen and hydroxyl to the 1,3,5-tri(4-pyridyl)benzene solution, and heat to react at a temperature of 160-180°C for a reaction time of 0.5-2h; After the reaction in S3 is completed, the solution is cooled and purified by column chromatography to obtain the electroplating copper leveler product.

5. The electroplating solution according to claim 4, characterized in that: The organic solvent in step S1 is one or more of ethylene glycol, propylene glycol, glycerol, and ethylene glycol monomethyl ether.

6. The electroplating solution according to claim 4, characterized in that The compound containing both halogen and hydroxyl in step S2 is 3-chloro-1-propanol, 2-chloroethoxyethanol or triethylene glycol monochlorohydrin.

7. The electroplating solution according to claim 4, characterized in that In step S2, the molar ratio of the compound containing both halogen and hydroxyl to 1,3,5-tri(4-pyridyl)benzene is (2.9-3.1):

1.

8. The electroplating method of the electroplating solution according to any one of claims 1 to 7, characterized in that: The current density during electroplating is 1-15ASD, and the electroplating temperature is 18-45°C.

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