Numerically Controlled Dry Etching Technology for Flattening of Si Wafer which Employs SF6/H2 Downstream Plasma

Abstract

Technology for the damage-free flattening of a Si wafer that employs a numerically controlled local dry etching (NC-LDE) technology has been developed to meet the requirement for achieving an extremely flat-surface wafer for the downscaling of ULSI feature size. In this technology, fluorine atoms which are generated in a localized SF6/H2 downstream plasma are exposed at a local area of a Si wafer, thereby generating a high etch rate of 130 µm/min at the bottom of the etched profile and a volume removal rate of 45.9 mm3/min. The flattening process was carried out by numerically controlled scan etching according to previously measured thickness data and consequently site flatness was improved from 0.51 µm to 0.08 µm within 150 s for a 200-mm-diameter Si wafer. This level of flatness will be the value required after 2005. Damage-free characteristics were also confirmed by minority carrier recombination lifetime and sub-surface defect measurements.