Microscopy studies for the deep-anisotropic etching of (100) Si wafers

Several etching phenomena appeared during the Si membrane process were observed and analyzed. In case of deep etching to above 300 µm depth, the etch-defects existed at the etched surface could be classified into three categories such as hillocks, adhered reaction products and white residues. It was known that the hillocks had a pyramidal shape or trapizoidal hexahedron structures depending on the density and size of the reaction products. Also, the existence of etch-defects and the etch rate distribution over a whole 4-inch wafers were investigated when the surfaces to be etched were downward, upward horizontally and erective for the stirring bar in the solution. As the results, the downward and erected postures were favorable in the etch rate uniformity and the etch-defect removal, respectively.