Plasma-Induced Damage and Its Control in Plasma Etching Processes

The pulse-time-modulated (TM) plasma could reduce the ultraviolet (UV) photon induced defects in SiO₂ film during the plasma etching process. In the TM plasma, the radio-frequency (RF) power for discharging plasma was modulated at a pulse-timing of a few tens microseconds. During the pulse-off period, UV photons radiation drastically decreased by reduction of electron energy in the plasma. As a result, UV photon-induced defects in SiO₂ film, such as E´ center, could be reduced in the case of using the TM plasma, as compared with CW plasma. Additionally, we found that the state of E´ center generated in the TM plasma had lower energy level than mat caused by the CW plasma. Then, lower temperature annealing was needed for the recovery of E´ center in the case of using TM plasma, whereas the CW plasma process needed higher temperature annealing These results clarified that the exciting state of UV photon-induced defects in SiO₂ film could be lowered by using the TM plasma.