Su Zifei,Shi Chunjing,Meng Fanning,Yang Ying,Yang Jinyao,Wang Zhihui,Wang Menghang,Cao Chun
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.
Zhang Linbo,Hong Mu-Nai Jin,Yang Ruoyu,Jiang Xianyu,Zhou Yusheng,Zhang Tongqing,Yuan Le
This study develops and explores a self-stratifying coating system that incorporates both epoxy and acrylic resins. It examines the impact of film thickness and substrate type on self-stratification behavior, confirms predictions from the surface energy model, and identifies the surface tension gradient as the primary driving mechanism for stratification. Additionally, this research investigates the influence of FeSiCr powder on the stratification behavior of the coating. Results demonstrate that the self-stratifying coating, composed of a blend of epoxy and acrylic resins with FeSiCr powder, exhibits superior corrosion resistance compared to coatings formulated solely from a mixture of epoxy resin and FeSiCr powder. SEM-EDS analysis reveals that the enhanced corrosion resistance can be attributed to the accumulation of epoxy resin and FeSiCr at the bottom of the coating, while the acrylic resin forms an effective protective layer on the surface. Furthermore, the study examines the effects of FeSiCr powder content, solvent addition, and volatilization rate on the stratified structure and appearance of the coating. The findings indicate that at relatively low FeSiCr powder content, the layered structure of the coating remains largely intact, with the powder predominantly residing within the epoxy resin layer. However, increasing the powder content compromises the self-stratification structure, leading to a rougher coating surface. It is also observed that augmenting the quantity of the xylene/butyl acetate mixture reduces pit formation on the surface, while the use of MIBK solvent results in incomplete stratification and exacerbates surface roughness.
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