UV photon-induced defect and its control in plasma etching processes

We found that the use of pulse-time-modulated (TM) plasma reduces ultraviolet (UV) photon-induced defects in SiO2 films formed during plasma etching. The pulse timing of the radio-frequency power in the TM plasma was modulated at a few tens of microseconds. During the pulse-off period, UV photon radiation significantly decreased because of reduced electron energy in the plasma. As a result, the density of UV photon-induced defects, such as E' centers, in SiO2 films was reduced when the TM plasma was used compared with that when a continuous wave (CW) plasma was used. In addition, we found that the energy level of excitation states of the E' centers generated in the TM plasma was less than that generated when the CW plasma was used. Low-temperature annealing was needed to reduce the number of E' centers when the TM plasma was used; whereas higher-temperature annealing was needed when the CW plasma was used. These results showed that the energy level of excitation states of UV photon-induced defects in SiO2 films was reduced by using the TM plasma