Illumination apparatus for semiconductor fabrication including conical optical means

摘要

A method of patterning a photoresist layer to provide an aperture having retrograde sidewalls is described. Illumination may be through a conical prism arrangement or a conical reflecting mirror and cylindrical mirror arrangement. The method includes the step of directing energy towards a mask which selectively exposes portions of a photoresist layer disposed on the substrate. The energy is directed to the mask at an oblique angle with respect to the normal to the surface of the substrate. The underlying photoresist layer is obliquely sensitized by the obliquely directed illumination. The portions of the layer which are obliquely sensitized are removed leaving behind an aperture having retrograde sidewalls. The retrograde sidewalls are a preferred photoresist profile for easy and reliable lift-off of deposited material from the semiconductor substrate.