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 SiO
₂
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 SiO
₂
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 SiO
₂
film could be lowered by using the TM plasma.