Nitrocellulose as a positive or negative self-developing resist

Abstract

Nitrocellulose functions as a self-developing resist when exposed to heavy ions (Ar+). However, when the resist is exposed to light ions (H+) the resist decomposes losing its nitrates and forming a nonvolatile residue. This residue consists primarily of carbon as determined by x-ray photoelectron spectroscopy (XPS). Nitrocellulose exposed to light ions, therefore, does not self-develop but forms a carbon-rich skin on the resist surface. These areas are protected by this skin during subsequent flood exposure with heavy ions, resulting in a negative resist image of the light ion exposure. The self-developing properties of nitrocellulose also make possible unique processing steps. One example is a dry lift-off. This has been accomplished by patterning the resist and evaporating metal onto the substrate and resist surfaces. The metal on the resist is lifted off with a jet of hot, dry nitrogen which volatilizes the resist and blows away the metal leaving only the metal previously deposited on the substrate.