Method of adjusting etch selectivity by adapting aspect ratios in a multi-level etch process

摘要

The present invention discloses a technique for controlling a local etch rate in forming multi-level contact openings, for example, in forming substrate contact openings and transistor contact openings of an SOI device. The aspect ratio dependent etch rate is correspondingly adapted by selecting in advance suitable aspect ratios for the contact openings so that the etch front may reach the respective final depth within a limited time interval.