Native Oxide Growth on Wafer Surface During Final Rinse

摘要

The effects of ambient and dissolved oxygen concentration in UPW on native oxide growth were studied at room temperature using a HF-cleaned silicon (100) surface. The studies were focused on the initial stage of the surface oxidation immediately after the HF-cleaning. The silicon surfaces were exposed to open air, to the UPW with different dissolved oxygen concentrations for a fixed duration, and dry nitrogen respectively. The SiO2 equivalent thickness of the native oxides formed on those surfaces were measured and compared. The results indicate that the ambient and the dissolved oxygen concentration in UPW dramatically affect the rate of the native oxide growth. Decreasing the dissolved oxygen concentration in UPW and performing the ultra-cleaning in an inert and dry ambient can reduce or eventually prevent the native oxide from growing. We used a high-resolution magnetic-sector based ICP-MS and found it to be an excellent tool for the low-level extractable Si determination. By coupling the rapid acid-etching process with HR-ICP-MS, one can measure the thickness of the oxides on a silicon surface at less than a monolayer range with a ≤0.1A resolution. This method can be utilized to monitor the native oxide growth on a silicon surface in the cleaning process. The data obtained should help optimize the cleaning processes and control the interface so that an ideal native oxide-free silicon surface can be produced.