Gas‐Phase‐Functionalized Plasma‐Developed Resists:Initial Concepts and Results for Electron‐Beam Exposure

Abstract

A resist method involving gas phase functionalization of exposed or unexposed resist by volatile inorganic compounds followed by pattern development using oxygen reactive ion etching is described for use in ion, photo, electron, and x‐ray lithography. Negative or positive tones can be obtained in theory from a single exposure by employing selective reaction of either the exposed or unexposed regions with volatile reactive inorganic compounds that form in situmasks during plasma development (usually as refractory metal oxides). Near surface functionalization (top several thousand angstroms) is seen as having resolution advantages for electron and photolithography. It is envisioned as being controlled by either limited permeation or by selective near‐surface exposure (i. e., low voltage ion or electron exposures). In electron lithography, this could reduce the proximity effect in backscatter‐limited thick resist films on high Z substrates. Consequently, we have studied materials and functionalizing reagents for electron lithography at 10 keV. The radiation‐initiated reactions studied in the resist were the creation and destruction of unsaturation (olefins, etc.). The inorganic functionalizing reagent was diborane. Pattern development was achieved using reactive ion etching. Thin (≤2000Aå) 1 μm line and space patterns were obtained at 10–50 μC/cm2 doses for materials which afforded negative and positive tones. These include chlorinated polyacrylates, polyisoprene, and copolymers containing unsaturation and chlorine functionality.