Polymer leveling agent and preparation method thereof, electroplating solution, electroplating method and product

Abstract

The invention discloses a polymer leveling agent and a preparation method thereof, an electroplating solution, an electroplating method and a product, and belongs to the technical field of copper electroplating. The leveling agent is obtained through reaction of a compound containing halogen and ether groups and 4-(dimethylamino) pyridine, the electroplating liquid comprises copper sulfate, sulfuric acid, chloride ions, an accelerator, an inhibitor and the leveling agent, the current density during electroplating is 1-15 ASD, and the electroplating temperature is 18-45 DEG C. The polymer leveling agent and the corresponding electroplating liquid provided by the invention can be used for electroplating copper columns and electroplating copper RDL, and the electroplating liquid does not need to be replaced when the same electroplating machine is used for producing and switching the copper columns or the copper RDL; meanwhile, the polymer leveling agent and the corresponding electroplating liquid provided by the invention can remarkably improve the copper electroplating effect, the obtained copper column and copper RDL are good in uniformity, the outline of the copper column is flat, and the performance requirement of semiconductor packaging can be met.

Description

Technical Field

[0001] The invention belongs to the technical field of electroplating copper, and relates to the preparation of copper pillars and copper redistribution layers for semiconductor packaging by electroplating methods, and specifically relates to a polymer leveler and a preparation method, an electroplating solution, an electroplating method and a product. Background Art

[0002] Copper pillar technology is a new generation of chip interconnection technology, which is used to connect the chip and substrate in the integrated circuit packaging process. It was first used by Intel in its 65 nm process microprocessor chip in 2006. Thanks to the characteristics of copper materials, copper pillars have excellent electrical conductivity, thermal performance and reliability, and can meet RoHS requirements. At the same time, the use of copper pillar technology can reduce the number of substrate layers in substrate design, thereby reducing the overall packaging cost. Compared with wire bonding, the overall packaging cost can be saved by about 20%. In addition, copper pillars have excellent electromigration characteristics and are particularly suitable for application scenarios that require high current carrying capacity. It is mainly used in high-end chip packaging and widely serves transceivers, embedded processors, power management, baseband chips, and application-specific integrated circuits (ASICs). In addition, copper pillars also meet the requirements of fine pitch, RoHS / green standards, low cost and good electrical performance, and are an ideal chip interconnection method.

[0003] Copper RDL (Redistribution Layer) is an advanced technology used in integrated circuit (IC) packaging. Its main function is to redistribute the input / output (I / O) of the chip to different locations on the chip. RDL consists of a copper metal layer and an insulating layer, and is commonly used in Fan-Out packaging, 2.5D, and 3D packaging. RDL plays a vital role in advanced packaging: it optimizes the placement of I / O pads so that pads originally located around the chip can be repositioned to more advantageous locations in the chip layout. With RDL, it is easier to add bumps to the chip, and in Fan-Out packaging, the use of RDL allows the number of I / Os to extend beyond the chip, increasing the number of I / Os.

[0004] Copper pillars and copper RDLs are usually prepared by electroplating. For example, CN111074306B discloses a copper pillar electroplating solution and electroplating process with ultra-high current density, and its formula is 150-240g / L copper methanesulfonate; 40-70g / L methanesulfonic acid; 30-50 mg / L chloride ion; 40-80 mg / L yanlu green; 2-5 mg / L polydisulfide dipropane sulfonate sodium; 40-100mg / L polyethylene glycol. Since copper methanesulfonate is used as a copper salt in this formula, its cost is relatively high, which greatly limits its production and use, and it is not possible to explain that the plating solution can be used to electroplate copper RDL. CN110577497B discloses an indanthrone quaternary ammonium salt polymer as a leveling agent for electroplating copper, which makes the electroplated particles finer and enables the copper-plated layer to obtain a high preferred crystal plane orientation. However, the leveling agent is a dye additive, which is easily decomposed during the electroplating process, limiting its application in industrial production. CN107541757B discloses a copper electroplating bath system containing a reaction product of a pyrazole polymer and a diepoxide polymer, which can achieve uniform copper column height and flat morphology, but does not describe that the bath can be used to electroplate copper RDL.

[0005] 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 the hole formed by the sidewall 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.

[0006] 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 polymers between copper and the metals on it, such as tin or nickel, during the welding process. Voids are formed 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. In the face of 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.

[0007] In addition, there are usually two types of electroplating solutions for copper pillars and copper RDLs on the market, using different additive systems. When the same electroplating machine is used to produce different products, the plating solution needs to be replaced, which makes maintenance more troublesome. Summary of the invention

[0008] The purpose of the present invention is to provide a polymer leveler and preparation method, electroplating solution, electroplating method and product. The polymer leveler and corresponding electroplating solution provided by the present invention can be used for electroplating copper pillars and copper RDLs. When the same electroplating machine is used to produce and switch copper pillars or copper RDLs, there is no need to change the plating solution. At the same time, the polymer leveler and corresponding electroplating solution provided by the present invention can significantly improve the copper electroplating effect. The obtained copper pillars and copper RDLs have good uniformity, and the copper pillars have flat profiles, which can meet the performance requirements of semiconductor packaging. The purpose of the present invention is achieved through the following specific technical solutions.

[0009] The primary aspect of the present invention is to provide a polymer leveler, the structure of which is shown in the following formula: .

[0010] In the formula, G is -O- or -O-CH2-CH2-O-; m is an integer between 0 and 6, n is an integer between 8 and 30, p and q are integers between 1 and 6, both inclusive; R1, R2, R5, R6, R7, and R8 are each selected from hydrogen or a straight-chain alkyl group having 1 to 4 carbon atoms, such as methyl, ethyl, n-propyl, and n-butyl; R3 and R4 are each selected from a straight-chain alkyl group having 1 to 4 carbon atoms, such as methyl, ethyl, n-propyl, and n-butyl; and X is Cl, Br, or I.

[0011] Preferably, the structure of the polymer leveler is one of the following formulae: , , , , , .

[0012] Another aspect of the present invention is to provide a method for preparing the aforementioned polymer leveler, comprising the following steps: S1. dissolving 4-(dimethylamino)pyridine in an organic solvent to obtain a 4-(dimethylamino)pyridine solution; S2: adding a compound containing both a halogen and an ether group to a 4-(dimethylamino)pyridine solution and heating for reaction; After the S3 reaction is completed, the solution is cooled to obtain a polymer leveling agent product.

[0013] The weight average molecular weight was determined by gel permeation chromatography (GPC). The relative molecular weight of the polymer was determined by using polyethylene glycol as a standard sample and an Agilent gel permeation chromatography (GPC) using a NOVEMA Max 100A gel chromatography column.

[0014] Furthermore, the organic solvent in step S1 is one or more of ethylene glycol, propylene glycol, glycerol, and ethylene glycol monobutyl ether.

[0015] Furthermore, the compound containing both halogen and ether groups in step S2 is dichloroethyl ether, 1,2-bis(2-chloroethoxy)ethane or bis(4-chlorobutyl)ether.

[0016] Furthermore, in step S2, the reaction temperature is 160-180° C., and the reaction time is 0.5-2 h.

[0017] Furthermore, in step S2, the molar ratio of the compound containing both halogen and ether group to 4-(dimethylamino)pyridine is (0.8-1.2):1.

[0018] 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 aforementioned polymer 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), the inhibitor is one or more of polyethylene glycol (PEG), polypropylene glycol (PPG), ethylene glycol propylene glycol block copolymers (PEO-PPO-PEO and PPO-PEO-PPO), and the weight average molecular weight of the inhibitor is in the range of 1000-10000.

[0019] 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.

[0020] 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.

[0021] Another aspect of the present invention is to provide an electroplated product obtained from the above electroplating solution.

[0022] Furthermore, the electroplating products include copper pillars and copper redistribution layers for semiconductor packaging.

[0023] The present invention has the following beneficial technical effects: the polymer 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

[0024] Figure 1 is a profile image of the copper pillar of Test Example 1.

[0025] Figure 2 is the RDL morphology profile of test example 1.

[0026] Figure 3 This is a profile image of the copper pillar of Test Example 2.

[0027] Figure 4 is the RDL morphology profile of test example 2.

[0028] Figure 5 This is a profile image of the copper pillar of Test Example 3.

[0029] Figure 6 is the RDL morphology profile diagram of test example 3.

[0030] Figure 7 is a profile diagram of the copper pillar of Test Example 4.

[0031] Figure 8 is the RDL morphology profile diagram of test example 4.

[0032] Fig. 9 is a profile image of the copper pillar of Test Example 5.

[0033] Fig.10 is the RDL morphology profile diagram of test example 5.

[0034] Fig.11 is a profile image of the copper pillar of Test Example 6.

[0035] Fig.12 is the RDL morphology profile diagram of test example 6.

[0036] Fig.13 is a profile image of the copper pillar of Test Example 7.

[0037] Fig.14 is the RDL morphology profile diagram of test example 7.

[0038] Fig.15 is a profile diagram of the copper pillar of Test Example 8.

[0039] Fig.16 is the RDL morphology profile diagram of test example 8.

[0040] Fig.17 It is a profile diagram of the copper column morphology of test comparative example 1.

[0041] Fig.18 It is the RDL morphology profile diagram of test comparative example 1.

[0042] Fig.19 This is a SEM image of the copper pillar + tin-silver electroplating of Test Example 1 after 10 reflows. DETAILED DESCRIPTION

[0043] 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

[0044] A polymer leveling agent, the chemical structural formula of which is: .

[0045] The preparation method is as follows: Add 30 mL of ethylene glycol to a two-necked flask equipped with a magnet and a condenser, heat to 80°C, then add 4.6 mmol of 4-(dimethylamino)pyridine, and after it is completely dissolved, add 4.6 mmol of dichloroethyl ether, heat to 170°C, and react at this temperature for 1 h. Allow the solution to cool to room temperature, dilute with deionized water and use directly. GPC determined that the weight average molecular weight of the polymer was Mw = 2431, the number average molecular weight was Mn = 2093, and the molecular weight distribution was 1.16. Example 2

[0046] A polymer leveling agent, the chemical structural formula of which is: .

[0047] The preparation method is as follows: Add 30 mL of ethylene glycol to a two-necked flask equipped with a magnet and a condenser, heat to 80°C, then add 4.6 mmol of 4-(dimethylamino)pyridine, and after it is completely dissolved, add 4.6 mmol of 1,2-bis(2-chloroethoxy)ethane compound, heat to 170°C, and react at this temperature for 1 h. Allow the solution to cool to room temperature, dilute with deionized water and use directly. GPC determined that the weight average molecular weight of the polymer was Mw=2912, the number average molecular weight was Mn=2503, and the molecular weight distribution was 1.16. Example 3

[0048] A polymer leveling agent, the chemical structural formula of which is:

[0049] The preparation method is as follows: Add 30 mL of ethylene glycol to a two-necked flask equipped with a magnetic rod and a condenser, heat to 80°C, then add 4.6 mmol of 4-(dimethylamino)pyridine, wait for it to completely dissolve, add 4.6 mmol of bis(4-chlorobutyl)ether compound, heat to 170°C, and react at this temperature for 1 h. Allow the solution to cool to room temperature, dilute with deionized water and use directly. GPC determined that the weight average molecular weight of the polymer was Mw = 2753, the number average molecular weight was Mn = 2432, and the molecular weight distribution was 1.18. Example 4

[0050] A polymer leveling agent, the chemical structural formula of which is:

[0051] The preparation method is as follows: Add 30 mL of ethylene glycol to a two-necked flask equipped with a magnet and a condenser, heat to 80°C, then add 4.6 mmol of 4-(dimethylamino)pyridine, wait for it to completely dissolve, add 4.6 mmol of bis(4-chlorobutyl)ether compound, heat to 160°C, and react at this temperature for 1 h. Allow the solution to cool to room temperature, dilute with deionized water and use directly. GPC determined that the weight average molecular weight of the polymer was Mw = 2712, the number average molecular weight was Mn = 2312, and the molecular weight distribution was 1.17. Example 5

[0052] A polymer leveling agent, the chemical structural formula of which is:

[0053] The preparation method is as follows: Add 30 mL of ethylene glycol to a two-necked flask equipped with a magnetic rod and a condenser, heat to 80°C, then add 4.6 mmol of 4-(dimethylamino)pyridine, wait for it to completely dissolve, add 4.6 mmol of bis(4-chlorobutyl)ether compound, heat to 180°C, and react at this temperature for 1 h. Allow the solution to cool to room temperature, dilute with deionized water and use directly. GPC determined that the weight average molecular weight of the polymer was Mw = 2806, the number average molecular weight was Mn = 2396, and the molecular weight distribution was 1.17. Example 6

[0054] A polymer leveling agent, the chemical structural formula of which is:

[0055] The preparation method is as follows: Add 30 mL of ethylene glycol to a two-necked flask equipped with a magnetic rod and a condenser, heat to 80°C, then add 4.6 mmol of 4-(dimethylamino)pyridine, wait for it to completely dissolve, add 4.6 mmol of bis(4-chlorobutyl)ether compound, heat to 170°C, and react at this temperature for 0.5 h. Allow the solution to cool to room temperature, dilute with deionized water and use directly. GPC determined that the weight average molecular weight of the polymer was Mw = 2561, the number average molecular weight was Mn = 2167, and the molecular weight distribution was 1.18. Example 7

[0056] A polymer leveling agent, the chemical structural formula of which is:

[0057] The preparation method is as follows: Add 30 mL of ethylene glycol to a two-necked flask equipped with a magnet and a condenser, heat to 80°C, then add 4.6 mmol of 4-(dimethylamino)pyridine, wait for it to completely dissolve, add 4.6 mmol of bis(4-chlorobutyl)ether compound, heat to 170°C, and react at this temperature for 2 h. Allow the solution to cool to room temperature, dilute with deionized water and use directly. GPC determined that the weight average molecular weight of the polymer was Mw=2819, the number average molecular weight was Mn=2403, and the molecular weight distribution was 1.17. Example 8

[0058] 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.

[0059] 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.

[0060]

[0061] 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.

[0062]

[0063] 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.

[0064] Table 1 Test conditions and results of test examples 1-8 and comparative example 1

[0065] 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 pillar morphology and RDL morphology of the comparative test example 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 16 It can be seen that after adding the polymer leveler synthesized by 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 2.9% and 4.1%, the copper pillars show slight depressions, and the TIR% is between -1.4% and -5.7%; the RDL line profile is flat, and the uniformity WID% in the chip is between 2.6-4.9%. Fig.17 , Fig.18 It can be seen that in the test comparative example 1, the polymer leveler synthesized by the present invention was not added, and the copper pillar after electroplating was seriously tilted and had a deep depression, and the RDL showed local burning and copper nodules on the surface. The electroplated copper pillar was subjected to tin-silver electroplating reflow 10 times, and its cross-sectional SEM image (magnification 5000 times) is as follows Fig.19 As shown, the picture shows that after 10 reflows, only a small amount of Kirkendall voids remain.

[0066] The results of the above test examples and comparative test examples show that the polymer 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 contours are flat, there are no appearance defects, and the uniformity is good (WID% <5%).

[0067] 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. A polymer leveler, characterized in that: Its structure is shown below: ， In the formula, G is -O- or -O-CH2-CH2-O-; m is an integer between 0 and 6, n is an integer between 8 and 30, p and q are integers between 1 and 6, both inclusive; R1, R2, R5, R6, R7, and R8 are each selected from hydrogen or a straight-chain alkyl group having 1 to 4 carbon atoms; R3 and R4 are each selected from a straight-chain alkyl group having 1 to 4 carbon atoms; and X is Cl, Br or I.

2. The polymer leveler according to claim 1, characterized in that Its structure is one of the following: ， ， ， ， ， 。 3. The method for preparing a polymer leveler according to claim 1 or 2, characterized in that: The following steps are involved: S1. dissolving 4-(dimethylamino)pyridine in an organic solvent to obtain a 4-(dimethylamino)pyridine solution; S2: adding a compound containing both a halogen and an ether group to a 4-(dimethylamino)pyridine solution and heating for reaction; After the S3 reaction is completed, the solution is cooled to obtain a polymer leveling agent product.

4. The preparation method according to claim 3, characterized in that: The organic solvent in step S1 is one or more of ethylene glycol, propylene glycol, glycerol, and ethylene glycol monobutyl ether.

5. The preparation method according to claim 3, characterized in that: The compound containing both halogen and hydroxyl in step S2 is dichloroethyl ether, 1,2-bis(2-chloroethoxy)ethane or bis(4-chlorobutyl)ether.

6. The preparation method according to claim 3, characterized in that: In step S2, the reaction temperature is 160-180° C., and the reaction time is 0.5-2 h.

7. The preparation method according to claim 3, characterized in that: In step S2, the molar ratio of the compound containing both halogen and ether group to 4-(dimethylamino)pyridine is (0.8-1.2):

1.

8. An electroplating solution, characterized in that Its components include: copper sulfate, sulfuric acid, chloride ions, an accelerator, an inhibitor and the polymer leveler according to claim 1 or 2, wherein 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.

9. The electroplating solution according to claim 8, 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.

10. The electroplating method of the electroplating solution according to claim 9, characterized in that: The current density during electroplating is 1-15ASD, and the electroplating temperature is 18-45°C.

11. An electroplated product obtained from the electroplating solution according to claim 9.

12. The electroplated product according to claim 11, characterized in that: The electroplating products include copper pillars and copper redistribution layers for semiconductor packaging.

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