(621dc) Kinetics of Carbon Elimination in Silicon Kerf Using Thermo-Gravimetric Analysis Estimations

Silicon wafer manufacture can be considered as an expensive and wasteful process. The Si saw dust (kerf) produced during slicing accounts for more than 40% of the initial ultrapure ingot material. Kerf is not recycled due to the inability to remove the impurities, such as carbonaceous content. The main contaminants present in kerf are carbon containing compounds, which can be removed by thermal processes. However, during the oxidation of the carbonaceous compounds by conventional thermal processes at high temperatures an undesirable side reaction resulting in silicon oxidation takes place simultaneously.  To optimize the recycling process it is paramount to study the kinetic dependence of carbon elimination and couple it with the kinetics of silicon oxidation

In this work we study the kinetic dependence of carbon elimination from kerf using Thermo-Gravimetric Analysis (TGA) both in air and inert gas atmospheres at low residence times. Three methods for determination of apparent activation energies are used and compared: the Ozawa-Flynn and Wall (OFW) method, the Kissinger-Akahira-Sunose (KAS) Method and the Kissinger method. A phenomenological power law model is used for defining the kinetic dependencies of reaction for the different atmospheres. Chemical characterizations including GC/MS, Raman spectroscopy and TC determinations are presented to suggest possible reaction mechanisms for the elimination of carbon from kerf. Finally, the model developed is compared with the results of carbon elimination from a novel bench scale Furnace Aerosol Reactor (FuAR). The FuAR process used for separating the domains of two global reactions: carbon removal and silicon oxidation, allow better control and effective removal of carbonaceous contaminants while reducing the oxidation of the silicon