CN-116837360-B - Electroless cobalt plating solution for filling nanoscale blind holes

CN116837360BCN 116837360 BCN116837360 BCN 116837360BCN-116837360-B

Abstract

The invention discloses an electroless cobalt plating solution for filling nano blind holes, which comprises the following raw materials of 11.5-33.5 g/L of cobalt chloride, 23.5-47.5 g/L of sodium citrate, 13.5-59.5 ml/L of hydrazine hydrate, 1.0-7.0 ml/L of triethanolamine, 1.0-5.0 mg/L of sodium polystyrene sulfonate and the balance of distilled water, wherein the pH value of the electroless cobalt plating solution is regulated to 12.0-13.0 by NaOH, and triethanolamine is taken as an accelerator and sodium polystyrene sulfonate is taken as an inhibitor. According to the invention, milligram-scale macromolecular inhibitor sodium polystyrene sulfonate is added into the electroless cobalt plating solution, so that no-cavity, seamless and perfect electroless cobalt filling of the nano-scale blind holes can be realized, the electroless cobalt plating solution is stable, and the deposited cobalt film has good quality.

Inventors

WANG ZENGLIN
SHEN YU
WANG LU
MA YI

Assignees

陕西师范大学

Dates

Publication Date: 20260508
Application Date: 20230621

Claims (4)

1. The electroless cobalt plating solution for filling the nano blind holes is characterized by comprising the following raw materials of 11.5-33.5 g/L of cobalt chloride, 23.5-47.5 g/L of sodium citrate, 13.5-59.5 ml/L of hydrazine hydrate, 1.0-7.0 ml/L of triethanolamine, 1.0-5.0 mg/L of sodium polystyrene sulfonate and the balance of distilled water, and regulating the pH of the electroless cobalt plating solution to 12.0-13.0 by NaOH.
2. The electroless cobalt plating solution for filling nano blind holes according to claim 1, wherein the electroless cobalt plating solution comprises the following raw materials of 14.0-26.5 g/L of cobalt chloride, 29.0-38.5 g/L of sodium citrate, 25.0-36.5 ml/L of hydrazine hydrate, 3.0-5.0 ml/L of triethanolamine, 2.0-4.0 mg/L of sodium polystyrene sulfonate and the balance of distilled water, and the pH of the electroless cobalt plating solution is adjusted to 12.5-12.8 by NaOH.
3. The electroless cobalt plating solution for filling nano blind holes according to claim 1, wherein the electroless cobalt plating solution comprises 18.0-20.0 g/L of cobalt chloride, 29-30 g/L of sodium citrate, 36-37 mL/L of hydrazine hydrate, 3.5-4.5 mL/L of triethanolamine, 2.0-3.0 mg/L of sodium polystyrene sulfonate and the balance of distilled water, and the pH of the electroless cobalt plating solution is adjusted to 12.5-12.8 by NaOH.
4. The electroless cobalt plating solution for filling nano-scale blind holes according to any one of claims 1 to 3, wherein the number average molecular weight of the sodium polystyrene sulfonate is 3000 to 5000.

Description

Electroless cobalt plating solution for filling nanoscale blind holes Technical Field The invention belongs to the technical field of filling of nano chip blind holes, and particularly relates to an electroless cobalt plating solution for filling nano blind holes. Background Currently, blind via filling of electroless copper plating solutions has been reported, and as electronic devices are developed toward miniaturization, multifunction, integration, the size of metal interconnect line width has broken through 7nm and even reached 2nm, and when copper interconnect lines are smaller than 7nm, the average free path growth of copper is faster, which causes the resistivity of copper interconnect lines to rapidly increase in an exponential fashion, and thus the resistivity of copper has been close to or even greater than that of cobalt. Therefore, in recent years, a large number of researchers have intensively studied metal materials with low resistivity and good conductivity, such as Co, ru and the like, and found that after the interconnection line width is less than 7nm, the resistivity of cobalt is low. The metal cobalt has the characteristics of low electron free range and difficult diffusion into an insulating layer, cobalt becomes a new generation of interconnection metal material, but the filling mode of cobalt interconnection is mainly performed by electroplating cobalt at present, the quality of a plating film is reduced due to easy hydrogen evolution when the cobalt interconnection is operated under an acidic condition, a plating solution is difficult to control in the operation process, and the filling of nano-scale blind holes of an electroless plating solution is hardly reported at present, so that the searching of the electroless cobalt plating solution is necessary to realize the filling of the nano-scale blind holes. Disclosure of Invention The invention aims to provide an electroless cobalt plating solution capable of realizing nano-scale blind hole filling, which improves deposition rate by adding triethanolamine, realizes nano-scale blind hole filling by adding sodium polystyrene sulfonate, and has lower resistivity of a coating formed by the electroless cobalt plating solution after deposition and better coating quality after heat treatment. Aiming at the purposes, the electroless cobalt plating solution adopted by the invention comprises the following raw materials of 11.5-33.5 g/L of cobalt chloride, 23.5-47.5 g/L of sodium citrate, 13.5-59.5 mL/L of hydrazine hydrate, 1.0-7.0 mL/L of triethanolamine, 1.0-5.0 mg/L of sodium polystyrene sulfonate and the balance of distilled water, and the pH value of the electroless cobalt plating solution is regulated to be 12.0-13.0 by NaOH. Further, the electroless cobalt plating solution is preferably prepared from the following raw materials of 14.0-26.5 g/L of cobalt chloride, 29.0-38.5 g/L of sodium citrate, 25.0-36.5 ml/L of hydrazine hydrate, 3.0-5.0 ml/L of triethanolamine, 2.0-4.0 mg/L of sodium polystyrene sulfonate and the balance of distilled water, wherein the pH value of the electroless cobalt plating solution is regulated to be 12.5-12.8 by NaOH. Further, the electroless cobalt plating solution is more preferably prepared from the following raw materials of 18.0-20.0 g/L of cobalt chloride, 29-30 g/L of sodium citrate, 36-37 mL/L of hydrazine hydrate, 3.5-4.5 mL/L of triethanolamine, 2.0-3.0 mg/L of sodium polystyrene sulfonate and the balance of distilled water, wherein the pH of the electroless cobalt plating solution is regulated to 12.5-12.8 by NaOH. The number average molecular weight of the polystyrene sodium sulfonate is 3000-5000. The beneficial effects of the invention are as follows: 1. The invention realizes the filling of the nano blind holes by using the chemical plating mode, does not need a seed layer before deposition, is suitable for large-scale deposition and has simple operation. 2. The invention uses hydrazine hydrate as reducing agent, the product is hydrogen and nitrogen, no impurity and no pollution, and the deposited cobalt plating film is pure. However, the deposition rate of the electroless cobalt plating solution taking hydrazine hydrate as a reducing agent is too low to achieve practical application, so that the deposition rate is improved by adding triethanolamine. After triethanolamine is added, the deposition rate is increased from 1.0 mu m.h -1 to 5.0 mu m.h -1, and the deposition rate is increased by about 5 times. 3. According to the invention, milligram-grade sodium polystyrene sulfonate is added into the electroless cobalt plating solution, so that concentration gradients are formed at the top and the bottom of the nano blind holes through diffusion, and the concentration gradients are converted into velocity gradients, so that perfect filling of seamless and void-free nano blind holes is realized. 4. The electroless cobalt plating solution obtained by the invention is stable and moderate in plating spe