Cr and CrO_x etching using SF₆ and O₂ plasma

Chromium is a frequently encountered material in modern nanofabrication, directly as functional (e.g., photomask generation) or indirectly hard mask to etch quartz). With the continuous downscaling of devices, control feature size patterned Cr and CrOx becomes increasingly important. etching typically performed using chlorine–oxygen-based plasma chemistries, but nanoscale imposes limitations. In this work, directional demonstrated for first time fluorine–oxygen-based plasma. Two cases are studied demonstrate performance: (i) mixture SF6 + O2 (ii) switching SF6/O2 procedure which plasmas used sequentially. The proposed performs with rates (ERs) up 400 nm/min at 300 W platen power highest when gas ratio ∼0.75%, i.e., almost pure profile shows reasonable directionality selectivity low, less than 5 toward Si, due high generated self-bias 420 V. can be improved lower power, accompanied considerable undercut. proceeds without need feed, and, therefore, ER reach much higher values (beyond 2000 W). As seems inadequate, sequential process while preserving directionality. achieved by relatively low (to ensure self-bias) separation controlled removal CrFx inhibiting species. Using such switched 30 beyond 20 good having an rate ∼1 nm per cycle (or 7 nm/min).