Residue removal after via-hole etching

Abstract

Using a combined microwave downstream plasma and low damage NE, we have successfully developed a dry process that removes both the photoresist and the remaining polymer residue after a via etch step.An ion assisted plasma process containing oxygen and fluorine was successfilly developed. It was found that the ion-assisted process converted the Ti, Si and their oxide containing residues to water-soluble compounds. Thus, a room temperature DI water rinse after the dry process removed the entire sidewall residue. The process is carried out at room temperature to avoid any undercutting of the TiN layer.SEM micrographs show that the via sidewall is free of any residue. The electrical data shows via resistance equal to or lower than samples cleaned with the standard process using oxygen plasma followed by a solvent clean. This process has been shown to be a reliable and cost-effective alternative to solvent based processing. Failure due to the narrow window of the solvent process is eliminated and equivalent or improved yield

Removal of the Metallorganic Polymer Residues Formed at Via Holes

“…For this reason, one of the most important aspects in the via hole cleaning process is the removal of this metallorganic polymer layer formed on the sidewalls and bottoms of via holes. 5 The cleaning process of the sidewall and bottom polymers of a via hole formed during RIE can be divided into three steps: ͑i͒ plasma dry ashing of the photoresist, ͑ii͒ wet cleaning of residual photoresist and polymer residues, and ͑iii͒ in situ Ar dry cleaning before upper metal sputtering. These post-RIE cleaning processes are ideally required to remove residual polymers completely before the metal gap filling.…”

“…Conventional removal of photoresist and RIE polymer residues was done using a two-step cleaning process which includes the ashing using an O 2 ͑or O 2 /N 2 ) plasma and the stripping using a hydroxylamine ͑HA͒-based chemical. 1,5 However, it was reported that the HA-based wet strip process did not completely remove the sidewall polymer formed in via holes with via etch-stopped on a TiN layer ͑VEST͒ structure. Therefore, in this study we investigated the effect of a post-RIE cleaning process using a non-HA-based stripper under various conditions to optimize the post-RIE residue removal.…”