Acidic copper electroplating leveling agent and application thereof

Abstract

The invention discloses an acidic copper electroplating leveling agent and application thereof, and belongs to the technical field of electroplating of integrated circuit packaging substrates. The molecular synthesis route of the leveling agent designed by the invention is simple, and the synthesis conditions are not harsh. The copper electroplating formula obtained by matching the leveling agent with other additives has high filling rate and high deep plating capacity for blind holes or through holes, the use concentration is low, and the operation window is large. 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 94.2%, and the surface copper thickness is 32.03 microns.

Description

Technical Field

[0001] The present invention belongs to the technical field of electroplating of integrated circuit packaging substrates, and specifically relates to an acidic electroplating copper leveling agent molecule and its application. Background Art

[0002] In recent years, high-density interconnect (HDI) technology has become one of the fastest-growing technologies in the printed circuit industry. For example, compared with standard multi-layer printed circuit boards, HDI allows more components to be installed on a printed circuit board (PCB) of the same area with fewer layers. Nano-scale or micro-scale blind vias with an extremely thin copper plating on the surface are one of the most practical methods for manufacturing HDI technology. The densification of HDI has significant advantages in terms of fast signal transmission, reduced size, reduced signal loss, and reduced cost per square inch of the printed circuit board. During the microvia metallization process, the superfilling of blind vias is generally considered to be efficient and high-performance, without voids or seams. To achieve highly reliable interconnections through a sulfate-based electrolyte system, electroplating additives have become the basic choice for via filling applications due to their convenient operation, low cost, safety, and easy waste treatment. Generally, additives such as inhibitors, accelerators, and leveling agents are the key to filling through-holes of different diameters and depths.

[0003] The leveling agent is also known as the second type of inhibitor, and its types are complex and diverse, including dye types, organic amine types, small molecules, and polymer molecules, etc. Adding a leveling agent to the copper plating solution can improve the dispersion ability and micro-leveling ability of the plating solution. Having micro-leveling ability means being able to fill in extremely small indentations or scratches on the substrate. The leveling agent can also increase the cathodic polarization and inhibit the deposition of copper ions, but the difference from the inhibitor is that the leveling agent can function without the assistance of Cl - which is related to the fact that all leveling agent molecules carry quaternary ammonium cations. The leveling agent is crucial for obtaining a uniform copper coating. For example, Chinese Patent Application CN110158124A discloses an electroplating copper leveling agent that can make the plating surface flat and prevent voids from occurring at the hole opening, but the synthesis steps of this leveling agent are complex, require a large concentration, and have a small operable range. Therefore, there is an urgent need to provide an acidic electroplating copper leveling agent with simple synthesis steps, low required concentration, and a large operation range. Summary of the Invention

[0004] Aiming at the problems existing in the background art, the purpose of the present invention is to develop a leveling agent with a simple synthesis route, excellent via filling performance, and a flat plating surface, and provide an acidic electroplating copper blind via filling formula in combination with other additives.

[0005] To achieve the above purpose, the technical solution of the present invention is as follows:

[0006] An acidic electroplating copper blind via filling formula, and the electroplating solution formula is composed of the following components:

[0007] 80 - 240 g / L of copper sulfate, 80 - 240 g / L of sulfuric acid, 30 - 100 mg / L of chloride ions, 0.05 - 10 mg / L of accelerator, 100 - 800 mg / L of inhibitor, 1 - 20 mg / L of leveling agent;

[0008] The inhibitor is polyethylene glycol, polypropylene glycol, block copolymer PEO - PPO - PEO or block copolymer PPO - PEO - PPO.

[0009] Furthermore, the accelerator is at least one of sodium 3 - (benzothiazole - 2 - mercapto) propane sulfonate, sodium 3 - mercapto - 1 - propane sulfonate, sodium thiazolinyl dithiopropane sulfonate or bis(3 - sulfopropyl) disulfide.

[0010] Furthermore, the chemical structural formula of the leveling agent is as follows:

[0011]

[0012] Furthermore, the electroplating process conditions for electroplating copper are: the current density is 0.1 - 10 A / dm 2 , the stirring rate is 0.5 - 10.0 L / min, and the electroplating temperature is 10 - 45 °C.

[0013] The mechanism of the present invention is as follows: The reactive functional group of the leveling agent is in the imidazole ring, and it has a strong electron - donating ability. During the copper deposition process, it tends to transfer electrons to the low - energy empty orbitals to form covalent bonds. The leveling agent has a strong adsorption energy for the following reasons: The N + ions in the molecule can act as active adsorption sites; the oxygen atoms in the molecule provide additional active adsorption centers; the molecular volume is relatively large, and the coverage area after adsorption is relatively wide. The above - mentioned advantages of the leveling agent enable it to effectively inhibit the deposition of copper ions outside the blind holes, thus ensuring a flat plating surface.

[0014] In summary, due to the adoption of the above - mentioned technical solutions, the beneficial effects of the present invention are:

[0015] The present invention provides a synthesis method of an acidic electroplating copper leveling agent, and together with other additives, an acidic electroplating copper blind - hole filling formula is obtained, which has the good effects of short hole - filling time and no voids in the holes. Using the formula of the present invention for electroplating blind holes with a diameter of 150 μm and a hole depth of 75 μm, the filling rate is 92.4%, and the surface copper thickness is 32.03 μm. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 It is the infrared absorption spectrum diagram of the leveling agent synthesized by the present invention.

[0017] Figure 2Metallographic micrograph of the blind hole section prepared in Example 1. Detailed implementation manners

[0018] 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 implementation manners and the accompanying drawings.

[0019] Example 1: Synthesis of the leveling agent L

[0020] Polymerization reaction was carried out using 1-vinyl-imidazole (VI) and pentaerythritol glycidyl ether (PGE) in a three-necked flask, and the mass ratio of the reactants was 1:1. The reaction was carried out in an N2 atmosphere, using ethanol and water as solvents, and the reaction was carried out at 353 K for 6 hours. After the experiment was completed, the residual solvent was separated by a rotary evaporator, and the product was washed with tetrahydrofuran, and finally the tetrahydrofuran was removed by rotary evaporation. The above process was repeated three times. When removing the residual solvent, the temperature of the rotary evaporator was set at 70 °C, and when removing tetrahydrofuran, the rotary evaporation temperature was room temperature. The infrared absorption spectrum of the obtained product is as Figure 1 shown.

[0021] Example 2

[0022] In this example, electroplating was carried out on blind holes with a diameter of 150 μm and a hole depth of 75 μm, including the following steps:

[0023] Step 1. Pretreatment of the circuit board with the above blind holes before electroplating. The specific process is: loading the board, degreasing, water washing, micro-etching, water washing;

[0024] Step 2. Prepare an electroplating copper bath solution: 200 g / L of copper sulfate pentahydrate, 50 g / L of sulfuric acid, 60 mg / L of chloride ions, 100 mg / L of inhibitor, 6 mg / L of accelerator, and 2 mg / L of leveling agent;

[0025] The inhibitor is a block copolymer PEO-PPO-PEO;

[0026] The accelerator is a mixture of sodium 3-(benzothiazole-2-mercapto) propane sulfonate and sodium polydithiopropane sulfonate (mass ratio 1:2);

[0027] The leveling agent is the leveling agent L synthesized in Example 1;

[0028] Step 3. Carry out electroplating: During electroplating, control the temperature at 25 °C, the electroplating duration is 60 min, use gas stirring at 2.5 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).

[0029] After electroplating, the metallographic section of the blind hole is as shown in Figure 2 Figure [Figure number not provided in the original]. It can be seen from the figure that the deep plating ability of this embodiment is 94.2%, and the surface copper thickness is 32.03 μm.

[0030] The above is only the specific implementation manner of the present invention. Any feature disclosed in this specification, unless specifically described, can be replaced by other equivalent or similar-purpose alternative features; all the features disclosed, 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. An acidic copper electroplating leveling agent molecule, and the structural formula of the leveling agent molecule is (Ⅰ).

2. Application of the leveling agent molecule according to claim 1 as a leveling agent in an electroplating solution.

3. An electroplating solution, characterized in that, Containing the leveling agent molecule according to claim 1.

4. The electroplating solution formulation according to claim 3, wherein the electroplating solution formulation 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, leveling agent 1 - 20 mg / L, inhibitor 100 - 500 mg / L; 5. The electroplating solution formulation according to claim 4, characterized in that, The accelerator is at least one of sodium 3-(benzothiazole-2-mercapto)propane sulfonate, sodium 3-mercapto-1-propane sulfonate, sodium thiazolinyl dithiopropane sulfonate or bis(3-sulfopropyl) disulfide.

6. The electroplating solution formulation according to claim 4, characterized in that, The inhibitor is polyethylene glycol, polypropylene glycol, block copolymer PEO-PPO-PEO or block copolymer PPO-PEO-PPO.

7. The electroplating solution formulation according to claim 4, characterized in that, 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 - 10.0 L / min, and the electroplating temperature is 10 - 45 °C.

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