A solution for electroless cobalt plating for nanoscale blind via filling

Abstract

The application discloses a kind of for nanoscale blind hole filling electroless cobalt solution, the electroless cobalt solution is made of the following proportion of raw materials: cobalt chloride 11.5~33.5g / L, sodium citrate 23.5~47.5g / L, hydrazine hydrate 13.5~59.5mL / L, triethanolamine 1.0~7.0mL / L, sodium polystyrene sulfonate 1.0~5.0mg / L, the rest is distilled water;And use NaOH to adjust the pH of the electroless cobalt solution is 12.0~13.0;Wherein triethanolamine is accelerator, and sodium polystyrene sulfonate is inhibitor.The present application can realize nanoscale blind hole's perfect electroless cobalt filling without cavity, without gap by adding milligram level macromolecular inhibitor sodium polystyrene sulfonate in electroless cobalt solution, and electroless cobalt solution is stable, and deposition cobalt film quality is good.

Description

Technical Field

[0001] This invention belongs to the field of nanochip blind via filling technology, specifically relating to a chemical cobalt plating solution for filling nanoscale blind vias. Background Technology

[0002] Blind via filling with electroless copper plating solutions has been reported. Due to the trend towards miniaturization, multifunctionality, and integration in electronic devices, the width of metal interconnects has exceeded 7 nm, even reaching 2 nm. When copper interconnects are smaller than 7 nm, the mean free path of copper increases rapidly, causing the resistivity of copper interconnects to increase exponentially. Therefore, the resistivity of copper is approaching or even exceeding that of cobalt. In recent years, many researchers have focused on studying metal materials with low resistivity and good conductivity, such as Co and Ru. They have found that cobalt has a lower resistivity when the interconnect width is less than 7 nm. Furthermore, cobalt has a low electron free path and does not easily diffuse into the insulating layer, making it a new generation of interconnect metal material. However, currently, cobalt interconnect filling is mainly achieved through cobalt electroplating. Electroplating is prone to hydrogen evolution under acidic conditions, which reduces the coating quality, and the plating solution is difficult to control during operation. In addition, there are almost no reports on nanoscale blind via filling with electroless plating solutions. Therefore, exploring electroless cobalt plating solutions to achieve nanoscale blind via filling is essential. Summary of the Invention

[0003] The purpose of this invention is to provide a chemical cobalt plating solution that can achieve nanoscale blind hole filling. This chemical cobalt plating solution improves the deposition rate by adding triethanolamine and achieves nanoscale blind hole filling by adding sodium polystyrene sulfonate. Furthermore, the coating formed by the deposition of this chemical cobalt plating solution has low resistivity and good coating quality after heat treatment.

[0004] To achieve the above objectives, the chemical cobalt plating solution used in this invention is composed of the following raw materials in the specified proportions: cobalt chloride 11.5–33.5 g / L, sodium citrate 23.5–47.5 g / L, hydrazine hydrate 13.5–59.5 mL / L, triethanolamine 1.0–7.0 mL / L, sodium polystyrene sulfonate 1.0–5.0 mg / L, with the remainder being distilled water; and the pH of the chemical cobalt plating solution is adjusted to 12.0–13.0 using NaOH.

[0005] Furthermore, the electroless cobalt plating solution of the present invention is preferably composed of the following raw materials in the following proportions: cobalt chloride 14.0–26.5 g / L, sodium citrate 29.0–38.5 g / L, hydrazine hydrate 25.0–36.5 mL / L, triethanolamine 3.0–5.0 mL / L, sodium polystyrene sulfonate 2.0–4.0 mg / L, with the remainder being distilled water; and the pH of the electroless cobalt plating solution is adjusted to 12.5–12.8 with NaOH.

[0006] Furthermore, more preferably, the chemical cobalt plating solution of the present invention is composed of the following raw materials in the following proportions: cobalt chloride 18.0-20.0 g / L, sodium citrate 29-30 g / L, hydrazine hydrate 36-37 mL / L, triethanolamine 3.5-4.5 mL / L, sodium polystyrene sulfonate 2.0-3.0 mg / L, and the remainder being distilled water; and the pH of the chemical cobalt plating solution is adjusted to 12.5-12.8 with NaOH.

[0007] The number average molecular weight of the aforementioned sodium polystyrene sulfonate is 3000–5000.

[0008] The beneficial effects of this invention are as follows:

[0009] 1. This invention utilizes chemical plating to achieve nanoscale blind hole filling, eliminating the need for a seed layer before deposition, making it suitable for large-scale deposition and simple to operate.

[0010] 2. This invention utilizes hydrazine hydrate as a reducing agent, producing hydrogen and nitrogen gases as products, free from impurities and pollution, resulting in a pure cobalt-plated film. However, the deposition rate of the chemical cobalt plating solution using hydrazine hydrate as a reducing agent is too low for practical applications. Therefore, triethanolamine is added to improve the deposition rate. After adding triethanolamine, the deposition rate increases from 1.0 μm·h. -1 Increased to 5.0 μm·h -1 The deposition rate increased by about 5 times.

[0011] 3. In this invention, milligram-level sodium polystyrene sulfonate is added to the chemical cobalt plating solution to create a concentration gradient at the top and bottom of the nanoscale blind holes through diffusion. This concentration gradient is converted into a rate gradient, thereby achieving seamless and void-free perfect filling of the nanoscale blind holes.

[0012] 4. The chemical cobalt plating solution obtained by this invention is stable and has a moderate plating rate. The method of using this solution to fill nanoscale blind holes is simple and low in cost. It also provides a new method and idea for realizing cobalt interconnects. Attached Figure Description

[0013] Figure 1 This shows the trend of deposition rate of the plating solution as a function of triethanolamine concentration after the addition of triethanolamine.

[0014] Figure 2 This shows the trend of deposition rate of plating solution with the concentration of sodium polystyrene sulfonate after adding sodium polystyrene sulfonate.

[0015] Figure 3 This is a cross-sectional SEM image of a nanoscale blind hole (width: 50 nm; depth: 500 nm) after being plated in the chemical cobalt plating solution of Example 1 for 12 min.

[0016] Figure 4This is a cross-sectional SEM image of a nanoscale blind hole (width: 100 nm; depth: 420 nm) after being plated in the chemical cobalt plating solution of Example 2 for 12 min.

[0017] Figure 5 This is a cross-sectional SEM image of a nanoscale blind hole (width: 100 nm; depth: 500 nm) after being plated in the chemical cobalt plating solution of Example 3 for 12 min.

[0018] Figure 6 This is a cross-sectional SEM image of a nanoscale blind hole (width: 100 nm; depth: 400 nm) after being plated in the chemical cobalt plating solution of Example 4 for 12 min.

[0019] Figure 7 This is a cross-sectional SEM image of a nanoscale blind hole (width: 200 nm; depth: 500 nm) after being plated in the chemical cobalt plating solution of Example 5 for 12 min. Detailed Implementation

[0020] The present invention will be further described in detail below with reference to the accompanying drawings and embodiments, but the scope of protection of the present invention is not limited to these embodiments.

[0021] Because the deposition rate of electroless cobalt plating solutions using hydrazine hydrate as a reducing agent is too low, this invention improves the deposition rate by adding triethanolamine. 19.0 g of cobalt chloride, 29.4 g of sodium citrate, and 36.5 mL of hydrazine hydrate were added to distilled water and mixed thoroughly. Then, 0, 1.0, 2.0, 3.0, 4.0, 5.0, 6.0, and 7.0 mL of triethanolamine were added respectively, and the volume was brought to 1 L with distilled water. The pH was then adjusted to 12.7 with NaOH to prepare the plating solution. Figure 1 It can be seen that the deposition rate increases after adding triethanolamine to the plating bath. Specifically, after adding 4.0 mL / L of triethanolamine, the deposition rate increases from 1.0 μm·h. -1 Increased to 5.0 μm·h -1 The deposition rate increased by about five times. Therefore, triethanolamine can be used as an accelerator for electroless cobalt plating solutions.

[0022] To achieve seamless and void-free filling of nanoscale blind holes, this invention adds milligram-level sodium polystyrene sulfonate to the chemical cobalt plating solution. 19.0 g of cobalt chloride, 29.4 g of sodium citrate, 36.5 mL of hydrazine hydrate, and 4.0 mL of triethanolamine are added to distilled water and mixed thoroughly. Then, 0, 1.0, 2.0, 3.0, 4.0, and 5.0 mL of sodium polystyrene sulfonate with a number-average molecular weight of 5000 are added respectively. The solution is then diluted to 1 L with distilled water, and the pH is adjusted to 12.7 with NaOH to prepare the plating solution. Figure 2 It can be seen that after adding 2.0 mg / L of sodium polystyrene sulfonate to the plating bath, the deposition rate increased from 5.1 μm·h. -1It dropped to 1.2 μm·h -1 Therefore, sodium polystyrene sulfonate can be used as a macromolecular inhibitor for filling nanoscale blind pores.

[0023] Example 1

[0024] 14.3g cobalt chloride, 23.5g sodium citrate, 25.1mL hydrazine hydrate, 3.0mL triethanolamine, and 1.0mg sodium polystyrene sulfonate with a number average molecular weight of 5000 were added to distilled water and mixed thoroughly. The mixture was then brought to a final volume of 1L with distilled water. The pH was adjusted to 12.5 with NaOH to prepare a chemical cobalt plating solution.

[0025] Example 2

[0026] 16.7g cobalt chloride, 26.5g sodium citrate, 25.1mL hydrazine hydrate, 3.0mL triethanolamine, and 1.0mg sodium polystyrene sulfonate with a number average molecular weight of 5000 were added to distilled water and mixed thoroughly. The mixture was then brought to a final volume of 1L with distilled water and the pH was adjusted to 12.6 with NaOH to prepare a chemical cobalt plating solution.

[0027] Example 3

[0028] 19.0g cobalt chloride, 29.4g sodium citrate, 36.5mL hydrazine hydrate, 4.0mL triethanolamine, and 2.0mg sodium polystyrene sulfonate with a number average molecular weight of 5000 were added to distilled water and mixed thoroughly. The mixture was then brought to a final volume of 1L with distilled water. The pH was adjusted to 12.7 with NaOH to prepare a chemical cobalt plating solution.

[0029] Example 4

[0030] 21.4g cobalt chloride, 32.4g sodium citrate, 36.5mL hydrazine hydrate, 5.0mL triethanolamine, and 2.0mg sodium polystyrene sulfonate with a number average molecular weight of 5000 were added to distilled water and mixed thoroughly. The mixture was then brought to a final volume of 1L with distilled water. The pH was adjusted to 12.7 with NaOH to prepare a chemical cobalt plating solution.

[0031] Example 5

[0032] 23.8g cobalt chloride, 35.3g sodium citrate, 58.2mL hydrazine hydrate, 5.0mL triethanolamine, and 3.0mg sodium polystyrene sulfonate with a number average molecular weight of 5000 were added to distilled water and mixed thoroughly. The mixture was then brought to a final volume of 1L with distilled water. The pH was adjusted to 12.7 with NaOH to prepare a chemical cobalt plating solution.

[0033] To demonstrate the beneficial effects of this invention, the chemical cobalt plating solutions of Examples 1-5 were used to fill nanoscale blind holes with different aspect ratios at 65°C. The results were characterized by cross-sectional field emission scanning electron microscopy. Figures 3-7See Table 1.

[0034] Table 1

[0035]

[0036] Depend on Figures 3-7 As shown in Table 1, the chemical cobalt plating solution of the present invention can achieve cobalt-filled nanoscale blind holes of different aspect ratios. Cross-sectional SEM reveals that all sizes of blind holes are perfectly filled without gaps or voids. Therefore, the chemical cobalt plating solution of the present invention can be used as a method for cobalt-filled blind holes.

Claims

1. A chemical cobalt plating solution for filling nanoscale blind holes, characterized in that: The electroless cobalt plating solution is composed of the following raw materials in the following proportions: cobalt chloride 11.5–33.5 g / L, sodium citrate 23.5–47.5 g / L, hydrazine hydrate 13.5–59.5 mL / L, triethanolamine 1.0–7.0 mL / L, sodium polystyrene sulfonate 1.0–5.0 mg / L, with the remainder being distilled water; and the pH of the electroless cobalt plating solution is adjusted to 12.0–13.0 with NaOH.

2. The chemical cobalt plating solution for filling nanoscale blind holes according to claim 1, characterized in that: The electroless cobalt plating solution is composed of the following raw materials in the following proportions: cobalt chloride 14.0–26.5 g / L, sodium citrate 29.0–38.5 g / L, hydrazine hydrate 25.0–36.5 mL / L, triethanolamine 3.0–5.0 mL / L, sodium polystyrene sulfonate 2.0–4.0 mg / L, with the remainder being distilled water; and the pH of the electroless cobalt plating solution is adjusted to 12.5–12.8 with NaOH.

3. The chemical cobalt plating solution for filling nanoscale blind holes according to claim 1, characterized in that: The electroless cobalt plating solution is composed of the following raw materials in the following proportions: cobalt chloride 18.0–20.0 g / L, sodium citrate 29–30 g / L, hydrazine hydrate 36–37 mL / L, triethanolamine 3.5–4.5 mL / L, sodium polystyrene sulfonate 2.0–3.0 mg / L, with the remainder being distilled water; and the pH of the electroless cobalt plating solution is adjusted to 12.5–12.8 with NaOH.

4. The chemical cobalt plating solution for filling nanoscale blind holes according to any one of claims 1 to 3, characterized in that: The number-average molecular weight of the sodium polystyrene sulfonate is 3000-5000.

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