Additional etching to decrease polishing time for shallow-trench isolation in semiconductor processing

Abstract

During formation of shallow-trench isolation (STI) structures during semiconductor processing, an additional oxide-reduction etching step is performed prior to chemical-mechanical processing. In one implementation wet-etching and/or sputter etch-back (SEB) is performed prior to applying a reverse-tone mask. In another implementation a wet etching step is performed after the reverse-tone mask is stripped. One significant result of each of these steps is a reduction in the height and width of at least some of the oxide horns that remain after the reverse-tone mask is stripped. As such, the oxide structures that need to be planarized during CMP will be smaller than those of the prior art. Moreover, since the resulting oxide structures that need to be planarized by CMP processing are smaller, the oxide layer can be initially applied at a smaller thickness than that of the prior art. As such, the duration of CMP processing can be correspondingly shorter, resulting in polished semiconductor wafer surfaces with greater uniformity than that provided by the prior art.