Observation of lateral diffusion at Si-SiO interface by PEEM using synchrotron radiation

Hirao, Norie; Baba, Yuji  ; Sekiguchi, Tetsuhiro  ; Shimoyama, Iwao   ; Honda, Mitsunori   ; Narita, Ayumi

The electrical properties of Si-based semiconductor devices such as SOI depend on the valence state of silicon at the Si-SiO interface. In order to observe valence states of a solid surface at nanometer scale, we have developed a photoelectron emission microscopy (PEEM) system combined with synchrotron soft X-ray. The samples investigated were micropattern of Si and SiO prepared by ion implantation. We have observed the chemical state at the Si-SiO interface and the lateral diffusion of the valence states, during the annealing. Compared to the previously reported longitudinal diffusion, two differences are found in the present lateral diffusion, i.e., (1) the diffusion temperature is lower than that of longitudinal diffusion by 300C, and (2) the intermediate valence states are absent at the Si-SiO interface. These differences are interpreted by the volatile property of SiO molecules, i.e., SiO released from surface during the diffusion.