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With downscaling of ultralarge-scale integrated (ULSI) devices, metal contamination-free Si surfaces are essential to realize the high performance of devices, since metallic contaminants cause electrical defects, device degradation, and yield losses. 1 In order to avoid the effect of metallic contamination on device electrical properties, metallic impurities should be reduced to below 1.0 ϫ 10 9 atoms/cm 2 on a Si wafer surface in the semiconductor manufacturing for 1 Gb DRAM. 2,3 The mechanism of adsorption and desorption of metallic impurities on Si wafer surfaces was interpreted based on the electrochemistry at the solid-liquid interface in research on metallic contamination by T. Ohmi, 1,4 H. Morinaga 5,6 and L. Mouche. 7 Two mechanisms for the adsorption and desorption of metallic impurities on a Si wafer surface are: (i) Noble metals having higher electronegativity than that of silicon, such as Cu, Ag, and Au, take electrons from the Si surface to form direct chemical bonds with the Si surface. It has been known that these metals could be removed from the Si surface in a solution with a higher oxidation-reduction (redox) potential than required to take electrons from the adhered metals, resulting in the metal ion dissolution. 5,6 (ii) Base metals, such as Fe, Ni, Cr, Al, Ca, Na, and K, having a lower electronegativity than Si, are easily ionized in solution and included in the native or chemical oxide on the Si surface. These metals are easily removed with the native or chemical oxide by a dilute HF treatment. 1 In this work, we investigated the cleaning efficiency of various chemical solutions for noble metals such as Cu, Ag, and Au on a Si wafer surface and derived a cleaning mechanism based on the experimental results and metal adsorption. We describe the metal adsorption mechanism based on measurements of metal particle growth on a Si surface, metal dissolution characteristics in chemical solutions depending on pH and redox potential values, the effects of metalinduced oxide (MIO) and chemical oxidation, and metal-oxide formation enthalpy.Finally, based on the results, we suggest an advanced, cost-effective wet cleaning process that is suitable for removing noble metals from Si surfaces below the 1.0 ϫ 10 9 atoms/cm 2 level as required for ULSI Si device technology. (100) wafers with a resistivity range of 7-15 ⍀ cm were used in this experiment. All blank Si wafers were precleaned by a successive cleaning of sulfuric acid-hydrogen peroxide mixture (SPM), diluted hydrofluoric acid (DHF), and post-UPW rinse for 10, 1. and 10 min, respectively, and blow dried in pure N 2 before initial metal contamination from solution. After preIn this study, the cleaning efficiency of various chemical solutions for noble metals such as Cu, Ag, and Au on Si wafer surfaces is investigated and the cleaning mechanism is interpreted based on the result and the metal adsorption mechanism. Cu adsorption behavior can be interpreted by both electrochemical metal particle deposition and inclusion in the metal-induced oxide grown d...

The Front Cover illustrates the capability of naphthoquinones to make the hybrid conjugation with cancer cells at nanomolar concentrations. Various types of cancer can be highly lethal, and recent research discloses that every year there are an estimated 8.2 million cancer deaths worldwide. The drug design and experimental results of this study clearly reveal that naphthoquinone derivatives could be potent anticancer agents against a number of cancer types. More information can be found in the Full Paper by Dong Jin Yoo et al. on page 532 in Issue 5, 2019 (DOI: 10.1002/cmdc.201800749).