Selective metal etching in metal/polymer structures

摘要

A differential material removal process wherein a selected material can be rapidly removed without adverse impact to surrounding layers of different materials. Ultraviolet radiation is used to selectively remove metal without adversely harming adjacent polymer layers, in a metal-polymer multilayer structure. The wavelength (100-400 nm) of the ultraviolet radiation and the energy fluence per pulse are selected so that the removal rate of metal due to thermal processes is significantly greater than the removal rate of the polymer by ablative photodecomposition. This can occur at an energy fluence per pulse level greater than that at which the etch rate of the polymer begins to level off. For example, copper of a thickness less than 5 microns is rapidly etched in one or two pulses while adjacent polyimide layers are substantially unetched by the application of ultraviolet pulses of wave-lengths 248-351 nm, at energy fluences per pulse in excess of approximately 3 or 4 J/cm2.