RIF plasma etching of a polyimide film with oxygen mixed with nitrogen trifluoride

Oxygen mixed with nitrogen trifluoride (NF3) was used as the gas source for the plasma etching to increase the etching rate of the polyimide (PI) film. In order to investigate the effects of NF3 addition, surfaces of the etched PI films were analyzed with various methods. From the results of x-ray photoelectron spectroscopy (XPS), the chemical bonding state of the etched PI surface with 30% NF3/70% O-2 plasma was similar to that of the surface prepared using 100% O-2 plasma. The results of FT-IR analyses showed that a pan of materials deposited on the etched PI film was soluble in chloroform and it contained carbonyl and ether compounds. Furthermore, the etching products were analyzed using quadrupole mass spectrometry (QMS) and gas chromatography. The main products were found to be H2O, HF, CO and CO2. In addition, CO/CO2 ratio was found to be related to the etching rate which depended on the NF3 concentration.