Multidimensional Force Cleaning of Impurities on the Surface of Silicon Wafer for the Downstream Product Processing of Integrated Circuits
摘要
Cleaning of silicon (Si) wafers has become the key process in integrated circuit (IC) manufacturing, improving the quality and usability of Si wafers. However, traditional cleaning slurries usually contain strong and corrosive acids and alkalis, resulting in the potential damages to the environment and operators, as well as corrosion to Si wafers and production of wastes. To solve this challenge, a novel green slurry was developed, including Sodium carbonate and Citric acid. Under the action of the developed slurry, Si wafers were treated via synergetic effect between interval ultrasonication and paddle stirring. Orthogonal tests were performed through adjusting the concentration of Sodium carbonate and Citric acid, and time and temperature of cleaning. Energy-dispersive spectroscopy (EDS) analysis has revealed that the surface impurities on Si wafers reach their lowest levels (Na < 0.3%, Fe < 0.15%) under specific processing conditions. These optimal conditions include a Sodium carbonate concentration of 12 wt.% and a Citric acid concentration of 10 wt.%. Additionally, the processing temperature should be maintained at 45 °C, with a duration of 50 min. Prior to and after cleaning, surface roughness Ra of Si wafer is reduced from 9.39 ± 0.38 to 5.56 ± 0.51 nm. Combining x-ray photoelectron spectroscopy (XPS) and Fourier transform infrared spectrometer (FTIR) analysis, these impurities, such as oxyacid, organics, metallic oxides and metal ions, were removed from the Si wafers under different acidic and alkaline environments, through chelation and redox reactions. Therefore, the developed green slurry and novel approach using chemical and ultrasonic composite fields provide new insights for the cleaning and manufacturing of Si wafers.