Profile control in dry development of high‐aspect‐ratio resist structures

Anisotropic etching for dry development of thick resist layers in oxygen‐based plasmas has been developed for two particular applications: trilayer resist for planarization of steep binary optics structures, and top surface imaged (silylated) resists for deep submicron lithography. To reduce linewidth degradation during etching of high‐aspect‐ratio resist structures, lateral etching and bow are minimized in two different reactors, a conventional parallel‐plate reactive ion etching (RIE) system and a low‐pressure, high‐ion‐density helicon etcher. In the conventional RIE system, C5H8, a polymer‐forming gas is added to the O2 feed gas to form a sidewall inhibition layer. In the helicon reactor, very low temperatures (−100 °C) are used to suppress sidewall etching. Different optimization conditions are found for trilayer resist etching and pattern transfer of silylated resist in the helicon reactor.