Formula of electrocoppering bath for packaging substrate

Abstract

The invention provides a formula of an electroplating copper bath for a packaging substrate, and belongs to the technical field of electroplating of integrated circuit packaging substrates. According to the formula, non-toxic and non-irritant polysorbate is innovatively selected as an inhibitor, and other components are matched and designed, so that the obtained electroplating copper bath formula has high filling rate and high deep plating capacity for blind holes or through holes, meanwhile, the formula is also environment-friendly, and the production cost is reduced. When the formula is adopted for electroplating the blind hole with the diameter of 150 microns and the hole depth of 75 microns, the filling rate can reach 97.2%, and the surface copper thickness is only 29.99 microns.

Description

Technical Field

[0001] The present invention belongs to the technical field of electroplating of integrated circuit packaging substrates, and relates to a copper electroplating solution formula for through holes or blind holes, specifically a copper electroplating bath formula for packaging substrates. Background Art

[0002] IC substrates are bridges that provide connections between IC chips and PCBs. As Moore's Law approaches its limit, 2.5D / 3D advanced packaging has emerged, and interposer boards play an important role in it. Generally, the Z-axis interconnection in three-dimensional packaging requires electrical and transmission signal interconnection through the hole metallization of through holes or blind holes. To achieve the longitudinal electrical interconnection conduction function of three-dimensional packaging, it is necessary to fabricate micro holes longitudinally on the interposer board and achieve void-free hole metallization. Currently, the hole metallization of through holes or blind holes with high aspect ratios usually adopts the copper electroplating filling mode.

[0003] The key to copper electroplating filling is to select a suitable copper electroplating bath. Acidic copper electroplating baths generally optimize their performance by introducing different chemical additives. For example, Professor Dou Weiping of National Chung Hsing University in Taiwan used PEG as an inhibitor, sodium polydithiopropane sulfonate (SPS) and sodium 3-mercapto-1-propane sulfonate (MPS) as accelerators, and Janus green and diazine black as leveling agents, (Wei-Ping Dow, Ming-Yao Yen, Cheng-Wei Liu, Chen-Chia Huang, Enhancement of filling performance of a copper plating formula at low chloride concentration, Electrochimica Acta, Volume 53, Issue 10, 2008, Pages 3610-3619.) and conducted a large number of studies on the copper electroplating filling of micro blind holes with different thickness-to-diameter ratios. However, the above system with PEG as an inhibitor has defects such as a thick deposition thickness on the copper plating surface, a narrow operating window for additives, and a low bath life, and is not suitable for large-scale production. CN102995076A discloses a copper electroplating solution for micro blind hole filling, which uses substances such as block polyethers, polyglycol ether copolymers, amine-blocked polyethers or polyvinylpyrrolidone as inhibitors in the copper electroplating solution, and cooperates with accelerators such as sodium polydithiopropane sulfonate or sodium 3-mercapto-1-propane sulfonate, leveling agents such as Janus green, and chloride ions to achieve the copper electroplating filling of blind micro holes with different aspect ratios in the electroplating process; CN113943956A discloses an arbitrary layer copper electroplating bath and method suitable for thin surface copper filling applications, and its formula contains a triblock polymer inhibitor composed of polyethylene glycol or propylene oxide (PO) and ethylene oxide (EO), an leveling agent of mercaptotetrazole benzene derivatives, and brighteners such as sodium 3-mercapto-1-propanesulfonate.

[0004] However, after plating with the above electroplated copper bath formula, the additives remaining on the surface of the substrate will have a significant impact on the subsequent electroplating process. In addition, the inhibitor used in the formula is a non-environmentally friendly chemical substance, which not only increases the water consumption during the electroplating process, but also leads to an increase in the cost of preparing copper interconnections. Specifically, the surface residues will affect the adhesion and uniformity of the plating layer, while the treatment of the inhibitor increases the complexity and cost investment in the wastewater treatment process. Summary of the Invention

[0005] Aiming at the problems existing in the background technology, the purpose of the present invention is to provide an electroplated copper bath formula for a packaging substrate. In this formula, polysorbate is innovatively selected as the inhibitor, and other components are designed in combination, so that the obtained electroplated copper bath formula has a high filling rate and high throwing power for blind holes or through holes, is environmentally friendly at the same time, and reduces production costs.

[0006] To achieve the above purpose, the technical solution of the present invention is as follows:

[0007] An electroplated copper bath formula for a packaging substrate, the electroplating solution formula is composed of the following components:

[0008] Copper sulfate 80 - 240 g / L, sulfuric acid 80 - 240 g / L, chloride ion 30 - 100 mg / L, accelerator 0.05 - 10 mg / L, inhibitor 100 - 800 mg / L, leveling agent 1 - 20 mg / L;

[0009] The inhibitor is a polysorbate mixture.

[0010] Further, the polysorbate mixture is a mixture mainly composed of different types of polysorbates; the types of polysorbates include polysorbate - 20, polysorbate - 40, polysorbate - 60, and polysorbate - 80.

[0011] Further, the accelerator is at least one of sodium 3-(benzothiazol - 2 - ylthio)propane sulfonate, sodium 3 - mercapto - 1 - propane sulfonate, sodium thiazolinyl dithiopropane sulfonate, or bis(3 - sulfopropyl) disulfide.

[0012] Further, the leveling agent is 1-(4 - hydroxyphenyl)-5 - mercapto - tetrazole compound.

[0013] Further, the electroplating process conditions of the electroplated copper bath are: the current density is 0.1 - 10 A / dm 2 , the stirring rate is 0.5 - 5.0 L / min, and the electroplating temperature is 10 - 55 °C.

[0014] The mechanism of the present invention is as follows: There is competitive adsorption between polysorbate and the accelerator. Strong convection intensity is beneficial to the adsorption of polysorbate, while weak convection intensity is beneficial to the adsorption of the accelerator. Moreover, the adsorption rate of polysorbate is relatively fast, and the adsorption rate of the accelerator is slow, thus ensuring the filling method from bottom to top. Cl - There is a synergistic inhibitory effect with polysorbate and can form polysorbate-Cu + -Cl - The complex adsorbs on the metal surface and then inhibits copper deposition. There is no obvious competitive adsorption phenomenon between the leveling agent and polysorbate, that is, the leveling agent will not weaken the inhibitory effect of polysorbate, which means that the leveling agent will not accelerate the copper deposition rate outside the blind hole, and the surface copper thickness will not increase.

[0015] In summary, due to the adoption of the above technical solutions, the beneficial effects of the present invention are as follows:

[0016] The present invention provides an electroplated copper bath formula for a packaging substrate, using non-toxic and non-irritating polysorbate as an inhibitor, which has the good effects of short hole filling time and no voids in the holes. When electroplating blind holes with a diameter of 150 μm and a hole depth of 75 μm using the formula of the present invention, the filling rate is 97.2%, and the surface copper thickness is 29.99 μm. Brief Description of the Drawings

[0017] Figure 1 It is a schematic diagram of a blind hole.

[0018] Figure 2 It is a metallographic diagram of a blind hole section prepared in Example 1.

[0019] Figure 3 It is a metallographic diagram of a blind hole section prepared in Example 2.

[0020] Figure 4 It is a metallographic diagram of a blind hole section prepared in Example 3. Detailed Embodiments

[0021] To make the objectives, technical solutions and advantages of the present invention clearer, the present invention will be further described in detail below in conjunction with the embodiments and the drawings.

[0022] Figure 1 It is a schematic diagram of a blind hole. In the figure, B is the depth of the hole, A is the depth of the plated copper, A / B is the filling rate, and C is the surface copper thickness.

[0023] Example 1

[0024] In this example, electroplating is performed on blind holes with a diameter of 130 μm and a hole depth of 75 μm, including the following steps:

[0025] Step 1. Perform pre-treatment before electroplating on the circuit board with the above blind holes. The specific process is: loading the board, degreasing, water washing, micro-etching, and water washing;

[0026] Step 2. Prepare the electroplating copper bath solution: 220 g / L of copper sulfate pentahydrate, 52 g / L of sulfuric acid, 60 ppm of chloride ions (provided by sodium chloride), 100 ppm of inhibitor, 6 ppm of accelerator, and 8 ppm of leveling agent;

[0027] The inhibitor is polysorbate - 20;

[0028] The accelerator is a mixture of sodium 3-(benzothiazol-2-ylthio)propane sulfonate and sodium polydisulfide propane sulfonate (mass ratio 1:2);

[0029] The leveling agent is 1-(4-hydroxyphenyl)-5-mercapto-tetrazole compound;

[0030] Step 3. Perform electroplating: Control the temperature at 25 °C during electroplating, the electroplating duration is 60 min, use gas stirring at 1.8 L / min, and the current density is 2 ASD (the double-sided surface area of the cathode test board immersed in the electroplating solution is about 68 cm 2 , and the power supply sets the current intensity at 1.37 A).

[0031] After electroplating, the cross-sectional metallographic diagram of the blind hole is as Figure 2 shown. It can be seen from the figure that the deep plating ability of this embodiment is 81.5%, and the surface copper thickness is 20.28 μm.

[0032] Example 2

[0033] This example electroplates blind holes with a diameter of 150 μm and a hole depth of 75 μm, including the following steps:

[0034] Step 1. Perform pre-treatment before electroplating on the circuit board with the above blind holes. The specific process is: loading the board, degreasing, water washing, micro-etching, and water washing;

[0035] Step 2. Prepare the electroplating copper bath solution: 220 g / L of copper sulfate pentahydrate, 52 g / L of sulfuric acid, 60 ppm of chloride ions, 100 ppm of inhibitor, 6 ppm of accelerator, and 8 ppm of leveling agent;

[0036] The inhibitor is polysorbate - 80;

[0037] The accelerator is a mixture of sodium 3-(benzothiazol-2-ylthio)propane sulfonate and sodium polydisulfide propane sulfonate (mass ratio 1:2);

[0038] The leveling agent is 1-(4-hydroxyphenyl)-5-mercapto-tetrazole compound;

[0039] Step 3. Electroplating: During electroplating, control the temperature at 25°C, the electroplating duration is 60 min, use gas stirring at 1.8 L / min, and the current density is 2 ASD (the double-sided surface area of the cathode test board immersed in the electroplating solution is about 80 cm 2 , and the power supply sets the current intensity at 1.6 A).

[0040] After electroplating, the cross-sectional metallographic diagram of the blind hole is as shown in Figure 3 . It can be seen from the figure that the deep plating ability of this embodiment is 97.2%, and the surface copper thickness is 29.99 μm.

[0041] Example 3

[0042] In this embodiment, electroplating is performed on blind holes with a diameter of 150 μm and a hole depth of 75 μm, including the following steps:

[0043] Step 1. Perform pre-treatment before electroplating on the circuit board with the above-mentioned blind holes. The specific process is: loading the board, degreasing, water washing, micro-etching, and water washing;

[0044] Step 2. Prepare the electroplating copper bath solution: 220 g / L of copper sulfate pentahydrate, 52 g / L of sulfuric acid, 60 ppm of chloride ions (provided by sodium chloride), 200 ppm of inhibitor, 6 ppm of accelerator, and 6 ppm of leveling agent;

[0045] The inhibitor is polysorbate-60;

[0046] The accelerator is a mixture of sodium 3-(benzothiazol-2-ylthio)propane sulfonate and sodium polydithiopropane sulfonate (mass ratio 1:2);

[0047] The leveling agent is 1-(4-hydroxyphenyl)-5-mercapto-tetrazole compound;

[0048] Step 3. Electroplating: During electroplating, control the temperature at 25°C, the electroplating duration is 120 min, use gas stirring at 1.8 L / min, and the current density is 1 ASD (the double-sided surface area of the cathode test board immersed in the electroplating solution is about 80 cm 2 , and the power supply sets the current intensity at 1.6 A).

[0049] After electroplating, the cross-sectional metallographic diagram of the blind hole is as shown in Figure 4 . It can be seen from the figure that the deep plating ability of this embodiment is 88.9%, and the surface copper thickness is 29.99 μm.

[0050] The above are only specific embodiments of the present invention. Any feature disclosed in this specification, unless specifically described, can be replaced by other equivalent or alternative features with similar purposes; all the disclosed features, or all the steps in any method or process, except for mutually exclusive features and / or steps, can be combined in any manner.

Claims

1. A plating copper bath formula for a packaging substrate, characterized in that, The electroplating solution formula consists of the following components: Copper sulfate 80 - 240 g / L, sulfuric acid 80 - 240 g / L, chloride ion 30 - 100 mg / L, accelerator 0.05 - 10 mg / L, inhibitor 100 - 800 mg / L, leveling agent 1 - 20 mg / L; The inhibitor is a polysorbate mixture.

2. The electroplating copper bath formulation for a packaging substrate according to claim 1, wherein, The polysorbate mixture is a mixture mainly composed of different types of polysorbates; the types of polysorbates include polysorbate - 20, polysorbate - 40, polysorbate - 60 or polysorbate - 80.

3. The electroplating copper bath formulation for a packaging substrate according to claim 1, characterized in that, The accelerator is at least one of sodium 3-(benzothiazol - 2 - ylthio)propane sulfonate, sodium 3 - mercapto - 1 - propane sulfonate, sodium thiazolinyl dithiopropane sulfonate or bis(3 - sulfopropyl) disulfide.

4. The electroplating copper bath formulation for a packaged substrate according to claim 1, wherein, The leveling agent is 1-(4 - hydroxyphenyl)-5 - mercapto - tetrazole compound.

5. The electroplating copper bath formulation for a packaging substrate according to claim 1, wherein The electroplating process conditions of the copper electroplating bath are as follows: the current density is 0.1 - 10 A / dm 2 , the stirring rate is 0.5 - 5.0 L / min, and the electroplating temperature is 10 - 55 °C.

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