Positive photoresist thermally stable compositions and elements having deep UV response with maleimide copolymer

摘要

Actinic (deep ultraviolet, ultraviolet and visible) light sensitive positive photoresist compositions containing a mixture of an alkali-insoluble photoactive compound capable of being transformed into an alkali-soluble species upon exposure to actinic radiation, in an amount sufficient to render the mixture relatively alkali insoluble and a polymer comprising an amount of -CO-NH-CO- groups, such as maleimide and especially maleimide-substituted styrene copolymers, sufficient to render the mixture readily alkali soluble upon exposure to actinic radiation are disclosed. The preferred copolymers include maleimide/styrene or alpha -methylstyrene in a 1:1 molar ratio. The preferred photoactive compound suitable for a positive photoresist composition responsive to deep UV actinic radiation has the formula 18-B in Table I. The present invention also contemplates photosensitive elements and thermally stable photochemically imaged systems based on the actinic light sensitive positive photoresist compositions. The positive photoresist compositions are coated onto a substrate to produce a photosensitive element, which upon exposure to a pattern of actinic radiation of wavelength in the range of about 200-700 nm produces a photochemically imaged system that can be treated with an alkaline developer to form highly resolved patterns, by highly selective removal of exposed areas. After development, preferred embodiments of the photochemically images systems exhibit insignificant changes in the highly resolved features (one micron) in the patterned image upon postbaking at temperatures of about 230 DEG C. and is, thereafter readily stripped. The high thermal stability exhibited by the photochemically imaged systems formed from the positive photoresist compositions of the present invention allows faster processing at higher temperatures, on equipment like plasma etchers and ion implanters; the developed photochemically imaged systems of the present invention retain high resolution, i.e., retain sharp, steep patterned image profiles.