Heat activated dry development of photoresist by means of active oxygen

Abstract

Heat activated method for developing and improving the definition of a patterned heat-photoresist layer as applied to a substrate surface of different material, such as a semiconductor slice, in the fabrication of an electronic structure or photomask, through the use of a reactive species of oxygen including monatomic oxygen or ozone in an oxygen-containing gas. A layer of photoresist material upon being selectively exposed to an energy source, such as ultraviolet radiation, X-ray, or E-beam radiation acquires a predetermined patterned definition therein because of chemical changes in the photoresist material which is photosensitive. After such selective exposure, the photoresist layer is characterized by a differential reactivity which is heightened by a chemical or a physical change occurring in either one of the exposed or unexposed portions of the layer of photoresist material enabling the selective removal thereof. In a preferred embodiment, the photoresist material is of a character undergoing a reduction in thickness in areas unexposed to the energy source which may be accentuated by a further heat treatment to produce regions of reduced thickness in the photoresist layer corresponding to the desired pattern. The regions of photoresist material of reduced thickness are then selectively removed from the layer of photoresist material by the differential reaction of the gaseous reactive oxygen species therewith to develop the pattern in the layer of photoresist material as defined by its selective exposure to the energy source.