Electronic copper electroplating solution containing single additive and application of electronic copper electroplating solution in copper electroplating

Abstract

The invention discloses an electronic copper electroplating solution containing a single additive and application of the electronic copper electroplating solution in copper electroplating, and belongs to the technical field of electroplating. The application in copper electroplating is characterized by comprising the following steps: sequentially adding sulfuric acid, hydrochloric acid and the single additive into an aqueous solution of anhydrous cupric sulfate to obtain an electroplating solution; and placing the electroplating solution in an electroplating bath, taking a phosphorus-containing copper plate as an anode, taking a to-be-electroplated sample as a cathode, switching on a power supply, and carrying out electroplating treatment, thereby completing the process. The invention discloses an innovative copper electroplating process, which is characterized in that 2-sulfydryl-1-methylimidazole is used as a single small molecule inhibitor to be applied to the whole copper electroplating process, and when the 2-sulfydryl-1-methylimidazole is used for obtaining blind hole copper electroplating filling without gaps and cavities in electroplating, no cavities and cracks are generated, and the stability and the reliability are excellent.

Description

Technical Field

[0001] This invention relates to the field of electroplating technology, and in particular to an electronic copper plating solution containing a single additive and its application in copper plating. Background Technology

[0002] As chip manufacturing processes continue to shrink, integrated circuit technology has evolved from an era centered on transistors to an era centered on interconnects. Electroplating copper is a crucial step in the manufacturing of core electronic devices such as printed circuit boards (PCBs) and integrated circuits (ICs). The uniformity, density, and flatness of the plating layer directly determine the signal transmission efficiency and lifespan of the device. Traditional additive-free plating solutions, due to uncontrolled copper ion deposition rates, tend to form rough, porous plating layers, which cannot meet the demands of increasingly sophisticated electronic devices. Additives, as the core of regulating plating performance, have driven the iteration from traditional systems to more efficient systems.

[0003] While the traditional three-additive system is the mainstream in industrial applications, it relies on the synergistic effect of inhibitors, accelerators, and leveling agents to achieve coating quality control. Generally, accelerators refer to small-molecule organic sulfides containing specific functional groups such as (-SS-), mercapto (-SH), and sulfonic acid (-SO3-), which can accelerate deposition at the bottom of pores. A common example is sodium polydisulfide dipropane sulfonate (SPS). Commonly used inhibitors are mainly macromolecular polyethers or polyols, such as polyethylene glycol (PEG). Compared with inhibitors, leveling agents can achieve a strong inhibitory effect with a very small amount added and are quickly deactivated, resulting in a smooth and flat coating surface. However, the three-additive system has problems such as difficulty in component matching, the need for precise matching of component concentrations, and the ease with which the plating solution can fail due to component imbalance during production. In addition, the cost of purchasing and testing multiple components is high, and the process complexity is significantly increased.

[0004] Single-additive systems focus on achieving multiple functions such as "inhibition, brightening, and leveling" with a single component, becoming a core direction for simplifying processes and reducing costs and increasing efficiency due to their outstanding advantages. These advantages are concentrated in three aspects: First, simplified process, eliminating the need to adjust the proportions of multiple components, requiring only control of the concentration of a single additive, significantly reducing the difficulty of production operations and minimizing coating defects caused by improper component compatibility; second, controllable cost, saving the costs of purchasing, storing, and testing multiple additives, and ensuring stable plating solution composition, reducing the difficulty of waste liquid treatment and meeting the requirements of green production; third, broad performance adaptability, such as polyvinylpyrrolidone which can simultaneously adjust the deposition rate and grain size, and sodium diphenylamine sulfonate which improves coating density while achieving leveling, already meeting the production needs of low- to mid-range electronic devices. In summary, developing electroplating solution systems containing only a single additive is essential. Summary of the Invention

[0005] The purpose of this invention is to provide a copper plating solution containing only a single additive and its application in copper plating. When used in electroplating, it can achieve seamless and void-free blind hole copper plating, without the generation of voids and gaps, and has excellent stability and reliability.

[0006] To achieve the above-mentioned technical objectives, the technical solution of the present invention is as follows: An electronic copper plating solution containing a single additive, wherein the single additive is 2-mercapto-1-methylimidazole.

[0007] The content of the single additive is 1-20 ppm.

[0008] The application of an electronic copper plating solution containing a single additive in copper plating includes the following steps: (1) First, sulfuric acid, hydrochloric acid and the single additive are added sequentially to an aqueous solution of anhydrous copper sulfate to obtain an electroplating solution; (2) Place the electroplating solution in the electroplating tank, use the phosphorus copper plate as the anode and the sample to be plated as the cathode, turn on the power, and carry out the electroplating treatment to complete the process.

[0009] In the electroplating solution obtained in step (1), the content of anhydrous copper sulfate is 100-400 g / L, the amount of sulfuric acid added is 20-30 mL / L, and the amount of hydrochloric acid added is 1-20 mL / L.

[0010] The sample to be plated is a test plate containing blind holes, the diameter of which is 100-130 μm and the depth of which is 60-100 μm.

[0011] Before electroplating, the phosphorus-containing copper plate and the sample to be plated are pretreated to remove surface oxides and contaminants.

[0012] The phosphorus content in the phosphorus-containing copper plate is 0.03-0.07%.

[0013] Compared with the prior art, the beneficial effects of the present invention are as follows: This invention discloses an innovative copper electroplating process, the core of which lies in applying 2-mercapto-1-methylimidazole as a single small molecule inhibitor throughout the entire copper electroplating process. This additive has significant advantages: it is inexpensive and readily available, exhibits outstanding environmental performance, demonstrates excellent stability during copper electroplating, and is not easily decomposed. By applying a system containing only this single additive to the acidic copper electroplating process, the molecular structure can be simplified, thereby significantly simplifying the additive system and significantly shortening the electroplating time. This innovative method enables defect-free filling of blind vias on printed circuit boards (PCBs), providing a strong guarantee for the efficiency and reliability of the electroplating process. Furthermore, the single-additive system facilitates in-depth research into the molecular reaction mechanism of the additive during acidic copper plating, providing important guidance for designing higher-performance environmentally friendly additives, optimizing additive composition, and developing new green copper plating technologies for application in the PCB field. Attached Figure Description

[0014] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0015] Figure 1 Metallographic diagram of blind vias (100*125μm) on an electroplated PCB test board with copper plating solution additives in Embodiment 1 of the present invention; Figure 2 Metallographic diagram of blind vias (100*125μm) of the electroplated PCB test board with copper plating solution additive in Comparative Example 1 of the present invention. Figure 3 Metallographic diagram of blind vias (100*125μm) on electroplated PCB test board with copper plating solution additive in Embodiment 2 of the present invention; Detailed Implementation

[0016] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0017] In the following embodiments, unless otherwise specified, the raw materials or processing techniques are conventional commercial products or conventional processing techniques in the art. Example 1

[0018] This embodiment provides an application of an electronic copper plating solution containing a single additive in copper plating, comprising the following steps: (1) Preparation of blind hole electroplating solution, the specific process is as follows: Take 400g of anhydrous copper sulfate and dissolve it in 800mL of ultrapure water. Take 30mL of concentrated sulfuric acid and slowly dilute it in 800mL of anhydrous copper sulfate aqueous solution. Then add 1mL of hydrochloric acid solution (mass fraction of 37%) to the solution. Finally, make up to 1L with ultrapure water to obtain 1L of basic electroplating copper solution. Place the basic electroplating solution in the electroplating tank and add 20ppm of 2-mercapto-1-methylimidazole using a pipette to obtain an electroplating copper solution containing additives.

[0019] (2) The anode copper plate containing phosphorus needs to be pretreated before use. The specific process is as follows: Immerse the test plate in 1 mol / L dilute sulfuric acid solution for 6 min to remove surface oxides, then rinse the test plate with ethanol for 1 min to remove contaminants on the surface of the anode plate, then rinse with deionized water for 2 min, and then wipe the water dry with lint-free paper to obtain the pretreated anode plate.

[0020] (3) Pretreatment of the cathode test plate: The specific process is as follows: Immerse the test plate in ethanol for 2 minutes to remove contaminants from the surface of the test plate, rinse it with deionized water, then immerse the test plate in 1 mol / L dilute sulfuric acid solution for 6 minutes to remove oxides on the surface of the copper layer, rinse it with deionized water, and finally dry it with a syringe. Attach the test plate to the front of the stainless steel plate with conductive adhesive, seal the surrounding area with insulating tape, and then waterproof it with transparent tape.

[0021] (4) The pre-treated test plate is used as the cathode, and the phosphorus-containing copper plate is used as the anode. The plate is placed in the electroplating solution, parameters are set, and the power supply is connected to complete the electroplating. The specific process is as follows: Pour the prepared electroplating solution into the electroplating tank. The pre-treated test plate is used as the cathode, and the phosphorus-containing copper plate is used as the anode. The positive terminal of the DC power supply is connected to the phosphorus-containing copper plate, and the negative terminal is connected to the test plate. The parameters are set according to the area to be plated and the current density. The air pump is turned on to continuously circulate air for stable stirring. For test plates with blind holes of 100um*125um, electroplating is completed after 60 minutes of power supply. The current density is 1.5A / dm³. 2 .

[0022] Depend on Figure 1 It is known that the novel plating solution system prepared using 2-mercapto-1-methylimidazole can achieve hole-free and defect-free filling of blind holes and gaps in PCB boards.

[0023] Comparative Example 1: This embodiment provides an application of an electronic copper plating solution in copper plating, the difference being that the selected additive (2-mercapto-1-methylimidazole) is not added to the electronic copper plating solution. Figure 2It is known that the blind hole filling effect is poor in the test plate electroplated in the electroplating solution without the additive (2-mercapto-1-methylimidazole). However, the addition of 2-mercapto-1-methylimidazole as a single additive can achieve seamless filling of blind holes, thus simplifying the electroplating solution system.

[0024] Comparative Example 2: The difference between this example and Example 1 is that, unlike the additive 2-mercapto-1-methylimidazole used in Example 1, this comparative example uses the existing additive polyethylene glycol 2000. The potentials of the different additives are shown in Table 1.

[0025]

[0026] As shown in Table 1, when the same concentrations of polyethylene glycol 2000 and 2-mercapto-1-methylimidazole were added, a constant current test (GMs) was used to simulate strong convection at 1600 rpm and weak convection at 100 rpm. When 2 ppm of 2-mercapto-1-methylimidazole was added at 200 s, the potential shifted negatively. Subsequently, 2 ppm was added every 100 s after 400 s, and then 2 ppm was added every 100 s. When the potential stabilized, Δη = η 1(100rpm) -η 2(1600rpm) =33.6mV. When 2-mercapto-1-methylimidazole is added until it stabilizes, the potential difference Δη > 0, indicating that the addition of 2-mercapto-1-methylimidazole increases cathodic polarization. 2-mercapto-1-methylimidazole adsorbs in the high-density region, strongly inhibiting copper electrodeposition and achieving perfect filling of micropores. The same procedure was followed with the addition of polyethylene glycol 2000, and the results are shown in Table 1, Δη = η. 1(100rpm) -η 2(1600rpm) =17.3mV. Comparing the two additives, when the same concentration of 2-mercapto-1-methylimidazole and polyethylene glycol are added, the potential difference when 2-mercapto-1-methylimidazole is added (33.6mV) is greater than the potential difference when polyethylene glycol 2000 is added (17.3mV). This indicates that the convection dependence of additive 2-mercapto-1-methylimidazole is better than that of polyethylene glycol 2000, and that additive 2-mercapto-1-methylimidazole has a better adsorption capacity on copper surfaces than polyethylene glycol 2000, showing potential for blind via filling applications. Example 2

[0027] Compared with Example 1, the electroplating parameters are the same, except that in this example, the concentration of anhydrous copper sulfate aqueous solution is 100 g / L, the concentration of sulfuric acid is 20 ml / L, the concentration of hydrochloric acid is 20 ml / L, and the concentration of additives is 1 ppm.

[0028] The filling result is as follows Figure 3 As shown, defect-free filling of blind holes is achieved, further illustrating the feasibility of the single-additive plating solution system of the present invention.

[0029] The foregoing description is intended to provide detailed embodiments for those skilled in the art, ensuring they can accurately grasp and apply the present invention. Any improvements or modifications to the present invention obtained by those skilled in the art through logical analysis, reasoning, or simple enumeration, without creative work, based on existing technology, should be considered within the scope of protection defined by the claims of this invention.

Claims

1. An electroplating copper bath containing a single additive, characterized in that: The single additive is 2-mercapto-1-methylimidazole.

2. The single additive containing electroplating copper plating solution according to claim 1, characterized in that: The content of the single additive is 1-20 ppm.

3. Use of an electrocopper plating bath containing a single additive according to claim 1 or 2 for electroplating copper, characterized in that The method comprises the following steps: (1) adding sulfuric acid, hydrochloric acid and the single additive into the aqueous solution of anhydrous copper sulfate in sequence to obtain an electroplating solution; (2) placing the electroplating solution in an electroplating tank, taking a phosphorus-containing copper plate as an anode and a sample to be plated as a cathode, connecting a power supply and performing electroplating treatment to complete the method.

4. Use of an electrocopper plating bath containing a single additive according to claim 3 for electroplating copper, characterized in that: In the electroplating solution obtained in step (1), the content of anhydrous copper sulfate is 100-400 g / L, the addition amount of sulfuric acid is 20-30 mL / L and the addition amount of hydrochloric acid is 1-20 mL / L.

5. Use of an electrocopper plating bath with a single additive according to claim 3 for electroplating copper, characterized in that: The sample to be plated is a test plate containing blind holes, the aperture of the blind holes is 100-130 um and the hole depth is 60-100 um.

6. Use of an electrocopper plating bath with a single additive according to claim 3 for electroplating copper, characterized in that: The phosphorus-containing copper plate and the sample to be plated are pretreated to remove surface oxides and contaminants before electroplating treatment.

7. Use of an electrocopper plating bath with a single additive according to claim 3 for electroplating copper, characterized in that: The content of phosphorus in the phosphorus-containing copper plate is 0.03-0.07%.

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