Physical and chemical changes in a polished wafer and in 2.5μm & 4μm epitaxially grown Si layer wafers (Epilayer wafer) after surface treatment were investigated. We characterized the influence of surface treatment on wafer properties such as surface roughness and the chemical composition and bonds. After each surface treatment, the physical change of the wafer surface was evaluated by atomic force microscopy to confirm the surface morphology and roughness. In addition, chemical changes in the wafer surface were studied by X-ray photoemission spectroscopy measurement. Changes in the chemical composition were confirmed before and after the surface treatment. By combined analysis of the physical and chemical changes, we found that diluted hydrofluoric acid treatment is more effective than buffered oxide etching for SiO2 removal in both polished and Epi-Layer wafers; however, the etch rate and the surface roughness in the given treatment are different among the polished 2.5μm and 4μm Epi-layer wafers in spite of the identical bulk structural properties of these wafers. This study therefore suggests that independent surface treatment optimization is required for each wafer type, 2.5μm and 4μm, due to the meaningful differences in the initial surface chemical and physical properties.

In this study, a new cleaning process with a low cost of ownership (CoO) was developed with ozonated DI water (DIO3). An ozone concentration of 40 ppm at room temperature was used to remove organic wax film and particles. Wax residues thicker than 200 Å remained after only a commercial dewaxer treatment. A DIO3 treatment in place of a dewaxer showed a low removal rate on a thick wax layer of 8000 Å due to the diffusion-limited reaction of ozone. A dewaxer was combined with a DIO3 rinse to reduce the wax removal time and remove wax residue completely. Replacing DI rinse with the DIO3 rinse resulted in a surface with a contact angle of less than 5˚, which indicates no further cleaning steps would be required. The particle removal efficiency (PRE) was further improved by combining a SC-1 cleaning step with the DIO3 rinsing process. A reduction in the process time was obtained by introducing DIO3 cleaning with a dewaxing process.