Highly selective etch process for submicron contacts

摘要

A method for forming contacts with vertical sidewalls, high aspect ratios, improved salicide and photoresist etch selectivity at submicron dimensions. In one currently preferred embodiment, an opening is formed in a dual oxide layer by etching the undoped oxide layer at a first rate and then etching the doped oxide layer at a second rate. The etch process is performed in a low density parallel plate reactor. The process parameters of the etch are fixed in ranges which optimize the etch process and allow greater control over the critical dimensions of the opening. For example, the oxide layer is etched at a pressure in the range of approximately 100-300 mTorr and with an etch chemistry having a CHF3:CF4 gas flow ratio in the range of approximately 3:1-1:1, respectively.