Low-temperature etching for deep-submicron trilayer resist

The effects of Cl 2 addition to O 2 plasma used for deep-submicron trilayer resist etching are investigated. The bottom-layer organic resist is etched using a low-temperature microwave plasma etcher. With O 2 +Cl 2 etching gas, highly anisotropic etching is achieved at higher temperatures than with pure O 2 . Cl 2 concentrations above 25% reduce resist selectivity relative to the SOG intermediate layer. Vertical 0.1-µm-wide resist patterns are achieved with O 2 +25% Cl 2 at -60°C. Broadened resist patterns with tapered side walls are produced at lower temperatures and at higher Cl 2 concentrations; this is thought to be caused by chlorine passivation and polymer deposition on the side walls.