Elimination of Carbon Contamination from Silicon Kerf Using a Furnace Aerosol Reactor Methodology

Abstract

Approximately 40% of the refined silicon is lost as sawdust (kerf) during the cutting process while producing wafers. Attempts have been made to recycle this kerf, but abundant impurities such as carbon (∼13000 ppm) burden its recovery. Using conventional bulk heating methods to remove carbon requires long residence time and inevitably causes silicon oxidation. This makes the treated kerf unsuitable for further processing and reuse. A novel aerosol method that is effective for selective carbon removal from silicon kerf at low residence times is described. The design of the aerosol process is supported by thermogravimetric analysis of kerf that provides insights into kinetics of the carbon removal process. At 900 °C in an air atmosphere carbon was removed below detection levels at a residence time of 6 s. Under the same conditions in a nitrogen atmosphere, 90% elimination of carbon was measured. Minimal oxidation of the Si sample was observed under these conditions.