Mechanism of Cloudy Surface Generation on Si Wafer Employing Numerically Controlled Local Dry Etching (NC-LDE)

概要

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A damage-free flattening technology for a Si wafer employing numerically controlled local dry etching (NC-LDE) was developed to meet the requirement of an extremely flat surface wafer which is necessary for downscaling of ULSI feature size. During development of NC-LDE, the cloudy surface generation on the Si surface occurred using a quartz discharge tube. This problem was solved by 1% H2 addition to SF6 in an Al2O3 tube. The drastic effect of this gas system was studied in the gas phase and on the surface to elucidate the origin of the cloudy surface. The reaction between SiF4 and oxygen atoms generated by fluorine atom etching of the quartz tube deposited nonvolatile SiOxFy compounds on the Si surface around the locally etched region just under the quartz tube. Scanning of F atom fluxes, which induced roughening of the surface masked by the compounds, caused generation of the cloudy texture. H2 addition to SF6 in the Al2O3 tube caused no deposition of the compounds on the Si surface, because a small amount of oxygen atoms liberated from the Al2O3 tube, whose etch rate was substantially low with F atoms, were scavenged by hydrogen atoms probably as H2O.
2004-01-15