Abstract
Oxygen mixed with nitrogen trifluoride (NF3) was used for the gas source of the plasma etching to improve the etching rate of the polyimide (PI) film.
In order to investigate this etching mechanism, the etching products were analyzed with quadrupole mass spectrometer (QMS), and gas chromatography. From these analyses, main products were assumed to be H2O, HF, CO, and CO2. Moreover, the CO/CO2 ratio was seemed to be related with etching rate depending on the NF3 concentration. In the PI etching mechanism, the cracking process of the benzene rings is seemed to be important. There would be a rate-limiting step in the PI cracking with O2 plasma. Formation of phenol groups would prevent breakdown of the benzene rings. On the other hand, this rate-limiting step would not exist in the breakdown process of benzene rings in the NF3/O2 plasma. The role of NF3 is predicted to construct oxygen addition sites and reproduce oxygen which is an etchant of the PI.
