Nearly Anhydrous Undissociated HF for the Removal of Hf / Ta / Zr Based Polymers after Plasma Etch, Selectively to Aluminum

Abstract

This paper investigates the possibility to fine tune a fluorinated solution to dissolve Ta, Zr, or Hf containing residues left after plasma etch, with maximum selectively towards silicon dioxide without corroding Aluminum. In this work amorphous "as dep" HfO 2 has been assumed and proven to be a valuable test vehicle to evaluate the chemistry ability to dissolve such residues selectively towards other materials. In solvent/water mixtures, HF doesn't significantly hydrate until water content is predominant in the mixture. Plus, High proton concentration is key to reach a good aluminum protection and significant HfO 2 dissolution rate in aqueous fluorinated solutions. By combining these properties an industrial solution has been engineered that achieves good dissolution of Ta, Zr, or Hf based polymers without corroding aluminum.

AlCu Pitting Prevention in Post Etch Cleaning

“…This pH shift generates two effects: on one side the limit of Al 2 O 3 dissolution reported in Pourbaix diagram is reached and, as a consequence, the amount of metallic Al exposed during the rinse is increased. On the other hand the speciation of fluorides is changed: the amount of undissociated HF, that in literature is reported to be the main responsible of Al 2 O 3 dissolution [4], is significanly increased compared to F-. As a consequence, also in this case the effect is the higher amount of Al metallic available that makes Cu reduction favourable.…”

Selective Removal of Various Resilient Ionic and Halides-Based Surface Contaminants by Wet Cleaning

“…The wet cleaner developed initially for post plasma etching removal of high K (Ta, Zr, Nb or Hf) based polymers was found to be extendable to tackle many additional industrial challenges [1]. The formulation is a fine tune of a strong acid, a solvent, and a fluorinated solution.…”