A study was conducted of preparation techniques for superhydrophobic and oleophobic surfaces by forming a roughened surface and preparing a hydrophobic monolayer, which never fills up the roughened surface when the roughned surface is coated by the monolayer. In this study, the techniques employed in preparation of the surfaces consisted of the following two steps. (1) Forming of a fractal-like structure on the surface of an aluminum substrate by sand-blasting and the electrolytic etching, wherein roughness was obtained at the microlevel by sand-blasting and further roughness was obtained at the nanolevel by the electrolytic etching after the sandblasting. (2) Modification of the roughened surface of the substrate with a HDFS (Heptadecafluoro-1,1,2,2-tetrahydrodecyl trimethoxysilane) monolayer, wherein the HDFS monolayer was prepared by means of a chemical adsorption technique, which provides a surface with the lowest surface energy surface on earth. The largest contact angles obtained with water and oil in this study were ϑw=152° and ϑo=135°, respectively. The optimum conditions of these roughnesses were ca. 150 μm with sand-blasting and tens of nm with electrolytic etching.
The present work is concerned with sulfidation of Cu, Zn and Ni containing plating wastewater with CaS. The sulfidation experiments were carried out by adding solid CaS (purity higher than 99%) to a simulated single-metal solution of NiSO4, ZnSO4 and CuSO4 solutions at a room temperature. At first, the experiments were conducted without pH adjustment and it was found that the complete sulfidation of Zn and Ni was achieved at an equimolar ratio of CaS to metal. For Cu, complete copper sulfidation was achieved at a CaS to Cu molar ratio of about 2 : 1. It was considered that CuS was almost instantly precipitated on the surface of un-dissolved CaS particles, which led to CaS being enclosed in CuS particles and it was thereby concluded that a higher CaS to Cu molar ratio was needed. This conclusion was further supported by a subsequent experiment, in which the sulfidation treatment was carried out using CaS solution. In this experiment, it was found that the concentration of Cu in the filtrate fell to below 1 mg/dm3 at an equimolar ratio of CaS to Cu. Finally, to investigate the possibility of selective precipitation, the experiments were conducted at fixed pH values and it was found that Cu was almost completely separated at pH = 1.8−2.0 when the CaS to Cu molar ratio was adjusted to 1 : 5. Further, almost 100% of Zn at pH > 4 and about 91% of Ni at pH = 7.5 was separated when an equimolar ratio of CaS to metal was used.
After the chemical mechanical planarization (CMP) processing of Cu wirings, defects are often observed and some of them induce problems in manufacturing large scale integrated circuit (LSI) devices. This investigation demonstrates that atomic force microscopy (AFM) is capable of performing in-situ nanoscopic visualization of initiation and growth processes of localized corrosion on the Cu wirings on LSI wafers in etching solutions of similar composition to the CMP process conditions. The AFM images indicate the presence of defects and dishings as a result of the CMP processing of the Cu wiring. The AFM analysis showed that defects and dishings became the starting points of pitting corrosion. The growth of corrosion is discussed in terms of cross-sectional and scaling analysis of AFM images. Moreover, the nanoscopic initiation and growth mechanisms of pitting corrosion and intergranular corrosion of Cu wiring are discussed based upon in-situ nanoscopic visualization by using AFM.