Characterization of a new cleaning method using electrolytic ionized water for polysilicon chemical mechanical polishing process

In trench isolation technology, the surface layers of poly-Si buried in the trench are contaminated with silica particles and chemical impurities by the conventional chemical-mechanical polishing (CMP) method. These contaminations produce some unexpected patterns and crystal defects in the wafer surface layer after oxidation. Furthermore, it is difficult to remove them by the conventional wet cleaning techniques. In this work, we have established a new post-CMP cleaning method, using electrolytic ionized water containing a small quantity of HCl. The anode water is shown to have a cleaning effect on the metallic and organic contamination, whereas the cathode water is shown to have a removing effect on the particles and an etching effect on the poly-Si surface. We present the optimization results of the post-CMP cleaning condition by investigating the surface-related properties by means of a particle counter, ellipsometry, secondly electron microscopy (SEM), atomic force microscopy (AFM), inductively coupled plasma/mass spectroscopy (ICP/MS), and secondary ion mass spectroscopy (SIMS). Our newly established cleaning method is currently applicable to the actual CMP planarization process for VLSI.