AVS 53rd International Symposium
    Plasma Science and Technology Friday Sessions
       Session PS1-FrM

Paper PS1-FrM11
Defect Generation due to UV Radiation in Plasma Etching Process

Friday, November 17, 2006, 11:20 am, Room 2009

Session: Plasma-Surface Interactions III
Presenter: Y. Ishikawa, Tohoku University, Japan
Authors: Y. Ishikawa, Tohoku University, Japan
A. Uedono, Tsukuba University, Japan
S. Yamasaki, National Institute of Advanced Industrial Science and Technology, Japan
S. Samukawa, Tohoku University, Japan
Correspondent: Click to Email
During the plasma process, plasma-induced ultraviolet (UV) photon generates the crystal defects in the dielectric films or in the interfaces. Especially in the SiO2 film, the UV photon generates the E' centers (Si dangling bond in the SiO2 film) in near the surface of the SiO2 film within 10 nm in depth. We had already reported that the E' center could be drastically reduced by using the pulse-time-modulated (TM) plasma. In this paper, we discussed the generation and restoration of defects during the TM plasma irradiation by using positron annihilation technique. In solid materials, the positrons are trapped at defects such as vacancy or voids with producing two 511 keV @gamma@-ray photons. To understand the situation of defects in detail, the Doppler Broadening of the @gamma@-ray photo-peak was evaluated using the S-parameter and W-parameter. S-parameter corresponds to the amount of the defects in the films, whereas, W-parameter corresponds to the electron energy distribution in the film. 500 nm of thermal SiO2 film were used, and irradiated to the Ar plasma. After the plasma irradiation, S-parameter in the case of irradiating TM plasma was the same as that in the case of using continuous wave (CW) plasma. Conversely, W-parameter after the TM plasma irradiation was much higher than that in the case of using CW plasma. These results indicate that the electron energy distributions in the SiO2 films after TM plasma irradiation are much different from that after CW plasma irradiation. Namely, different kinds of crystal defect were generated in both plasma. This result also suggests that the defects generated by TM plasma irradiation might be unstable than that generated by CW plasma. Consequently, it is speculated that the defects generated by TM plasma irradiation are easily restored through the thermal annealing. As a result, the TM plasma is much effective to eliminate generating defects due to UV irradiation during the etching processes.