Characterization of iodoheptafluoropropane as a dielectric etchant. I. Process performance evaluation

1- and 2-iodoheptafluoropropane were characterized extensively as potential replacement etchants for perfluorocompounds used in an oxide etch applicat ion. In the present study, via holes of critical dimension down to 0.35 mum were etched in an inductively coupled high density plasma tool. Oxide etch rate, mask and stop layer selectivities, and feature profile were among th e principal metrics used to evaluate the performance of these compounds. A conventional (C3F8-based) etch process was used as a reference. Process beh avior as a function of a number of variables-namely source power, bias powe r, etch gas flow, additive gas CH3F) flow, roof, wall, and chiller temperat ures, and pressure was studied. While good etch rates and feature profiles were obtained, mask and stop layer selectivity was found to be limited. As a supplement to the experimental work, a set of ab initio quantum chemical calculations was undertaken to obtain enthalpies of dissociation for each o f the bonds in the iodoheptafluoropropane molecules in order to better unde rstand their dissociation pathways in plasma environments. Part I focuses o n trends in process behavior as a function of the variables explored and di scusses key mechanisms responsible for the observed effects. Parts II and I II will focus on deposited film characterization and global warming emissio ns, respectively. (C) 2001 American Vacuum Society.