FT-IR-ATR study of depth pro®le of SiO2 ultra-thin ®lms

It is very important to characterize the depth change in chemical bonding structures of ultra-thin SiO2 ®lms. The LO mode and the lower frequency shoulder peak of SiO2 on Si was detected by the FT-IR-ATR method, and this band was simulated by a gradient layered and effective medium model. Interface roughness estimated from the shoulder bands of ATR spectra was in good agreement with the GIXR results, and the shoulder band also re¯ects the change of Si±O±Si bonding angle. In our calculation, the shoulder band around 1150±1050 cmÿ1 re¯ects the interface roughness and the shoulder band around 1250± 1150 cmÿ1 includes information about the change of Si±O±Si bonding angle and/or Si±O force constant. The FT-IR-ATR method is a useful technique with which to characterize SiO2 ultra-thin ®lms. # 2001 Elsevier Science B.V. All rights reserved.