Pulsed ultraviolet laser interactions with organic polymers—Dependence of mechanism upon laser power

Abstract

The interaction of pulsed, ultraviolet laser radiation with organic polymer films leads to ablation and etching of the surface provided the fluence of the pulse (which is of less than 1 μs duration) exceeds a threshold value. Precise etching of polymers such as polyimide using ultraviolet laser pulses from excimer lasers has developed into a useful technology especially in the microelectronics industry. It has now become possible to extend these interactions to the microsecond regime. The source of the pulses of 1–1000 μs duration is a continuous wave ion laser which is coupled to a mechanical chopper of variable speed. Microsecond pulses are also capable of etching polymers such as polyimide, poly(ethylene terephthalate) and poly(methyl methacrylate) precisely and with as little thermal damage as when nanosecond ultraviolet pulses are used. However, the mechanism of the interaction appears to be entirely different. Possibly chemical pathways for these interactions of photons with polymers are discussed.