Oxide dual damascene trench etch profile control

A systematic study of trench profile evolution in a medium-density oxide et ch reactor is presented. A Langmuir site balance model is developed in the limit of unity sticking coefficient which exhibits a flat etch front as is frequently required for dual damascene applications. The model indicates th at it is desirable to operate in a neutral-limited ion-assisted etch regime . Physical sputtering is also shown to be necessary, but this etch contribu tion must be kept small with respect to the ion-assisted etch rate. The mod el also indicates how either microtrenching or bottom rounding may be contr olled or avoided altogether. Model predictions are compared with experiment al data obtained from a Lam Research 4520XLE medium density reactor. This w ork includes a study of the trench bottom rounding dependencies upon pressu re, etch time, aspect ratio, and process gas flow for a fluorocarbon-based etch process. The model is shown to qualitatively capture experimentally ob served process trends. In some regimes, good quantitative agreement with ob served measurement is seen. It can thus serve as a useful guide fur trench etch process development. (C) 2001 The Electrochemical Society.