Pulsed CO2 laser etching of polyimide

Etching of thin polyimide films in air was investigated using a line tunable, pulsed CO2 laser. The threshold fluence for etching at a wavelength of 944 cm−1 (10.6 μm) exceeds that at 1087 cm−1 (9.2 μm) by a factor of 4. This is consistent with the infrared absorption spectrum which shows polyimide to be significantly more absorbing at 1087 cm−1. As a result, etching at 1087 cm−1 produces a cleaner, more precisely defined region. Analysis of the vapors generated during laser etching shows the simple gases CO2, H2O, and CO to be present.