Microscopic observation of lateral diffusion at Si-SiO interface by photoelectron emission microscopy using synchrotron radiation

放射光を用いた光電子顕微鏡によるSi-SiO界面の横方向拡散の顕微観察

平尾 法恵; 馬場 祐治  ; 関口 哲弘  ; 下山 巖   ; 本田 充紀*

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

放射光軟X線と光電子顕微鏡を組合せることにより、化学結合状態をナノスケールで画像観察する装置を開発し、同装置をSi-SiO界面の化学結合状態解析に応用した。SiとSiOから成る試料を加熱し、Si-SiO界面の表面拡散の観察を行った結果、縦方向の拡散と異なることがわかった。また、拡散中の界面にはSiO(Si)など中間の化学状態が存在しないという結果が得られた。これは拡散過程において揮発性のSiOが表面から脱離するためであると結論した。

The lateral surface diffusion at Si-SiO interface has been observed at nanometer scale using photoelectron emission microscopy (PEEM) combined with synchrotron soft X-ray excitation. The samples investigated were Si-SiO micro-patterns prepared by O ion implantation in Si(0 0 1) wafer using a mask. The lateral spacial resolution of the PEEM system was about 41 nm. The brightness of each spot in the PEEM images changed depending on the photon energy around the Si -edge, in proportion to the X-ray absorption intensity of the corresponding valence states. It was found that the lateral diffusion occurs at lower temperature than that reported for the longitudinal diffusion at the Si-SiO interface. It was also found that no intermediate valence states such as SiO (Si) exist at the Si-SiO interface during the diffusion. The observed differences between lateral and longitudinal diffusion are interpreted by the sublimated property of silicon monoxide (SiO).