Study of selective etching of TaN with respect to SiOCH dielectrics using SiF4 plasma processes

Abstract

TaN is used as a Cu diffusion barrier during metal interconnect formation to enable modern chip fabrication. In this study, the selective removal of TaN with respect to SiOCH dielectrics is explored using neutral dominant plasmas containing pure SiF₄ or with O₂ or H₂ additives. SiF₄ is studied because the Si-containing gas has been historically used to deposit Si-based films, but the gas also contains F capable of volatilizing Ta. This work explores the possibility of enabling both selective etching of TaN and selective deposition on SiOCH. SiF₄ discharges are impacted by the addition of O₂ and H₂ gases; exhibiting significantly different deposition and etching regimes. The substrate temperature plays a critical role in modulating the TaN etching versus deposition window compared to SiOCH. Through this work, selective etching of TaN with respect to SiOCH is achieved.