Generation and reduction in SiO2/Si interface state density during plasma etching processes

During plasma processes, the SiO2/Si interface state is generated by UV photon irradiation. We measured P-b centers (Si dangling bond at SiO2/Si interface) in SiO2/Si film by electron spin resonance spectroscopy. The density of P-b centers increased with increasing UV photon energy. This result indicates that high-energy photons effectively generate P-b centers because of the absorption at the SiO2/Si interface. At the same time, we found that UV photon flux is also an important factor in increasing the density of P-b centers. On the other hand, ion irradiations were not a significant factor in the generation of P-b centers. Ions can penetrate only the surface (less than 5 nm) but they cannot induce a P-b center at the SiO2/Si interface. Furthermore, pulse-time-modulated plasmas were used to reduce the UV photon irradiation during the plasma processes. The reduction in UV photon irradiation could completely eliminate the P-b centers compared with the use of a conventional continuous wave plasma. (c) 2008 American Institute of Physics.